# Summer Research Journal

#### Monday, June 3rd, 2002

It's the first day of summer research, there are 6 people working in the lab, two of them are here for the REU physics program. Basically, we talked general things about doing research here, and I have to finish up my incomplete WISE187 report, so I have to take a look at what I wrote on the report, and change it to make it perfect. Besides that, I was reading the book called "LINUX in 10 Minutes", it's very easy to understand, and I read about 4 chapters. About 4:00PM I left the lab.

#### Tuesday, June 4th, 2002

Second day of research, again, I was reading the book about LINUX, I think it's a great book, and then I started to think about what I have to do for the WISE report and learning the LINUX command, also HTML commands. I like to work with computers, so I enjoyed learning those. Also I decided to come here in the morning and after classes, oh well...I think I "have to" come after classes anyway, otherwise I will be delaying so much on my project while everyone else has a great result already. Well...I guess I really have to sacrifice my sleep sometimes. @_@

#### Wednesday, June 5th, 2002

Today I first started to edit my WISE report. When I wrote the report last semester, I had less knowledge about this topic than I do now. Therefore, there were things I wrote in the report that reflects my misunderstanding. It mainly was on the the explanation on my graph and the data. I did few search on the web about the laws we found out and things relates to my topic. I found the general function for Power Law and Zipf's Law:

Power Law ==> Y= CX^n
Zipf's Law ==> Pn ~ 1/(^a)

After discussing with Dr. Noe, we found out that even Zipf's law has the similar graph like power law does, it's mostly for statistical use, which is irrelevant for my graph and data. On the other hand, Power Law is most likely the right function I should look up; I also need to find some informations about hyperbolic graphs.
Dr. Noe also found a book talking about 80/20 rules, which mentioned power law in their data distribution for network linking. It's very interesting, but this book didn't mention much useful information.There was one thing mentioned in the book that their data is "scale free", and it means that any segment of data selected to be looked at obeys the functionality(??) of the graph or any laws the graphs implies to.

##### Little Notes...

I'm getting used to the LINUX system more and more everyday. Also, I have learned more about emacs commands, and am getting used to them more and more.(I think it took me months to be familiar with the system @_@)
photoluminescence => The excitation is caused by electromagnetic radiation.(From the book "Luminescence Screens.")

• Look up web for information about photoluminescence, try to find books in the library about it.

#### Thursday, June 6th, 2002

Today, while I was here this morning, I was surfing on the web and in the school library system trying to find information about "photoluminescence", "luminescence", "phosphorescence", "Power Law", and etc. In the school library system I found few books that might be useful for myself as reference, but 4 out of 6 books are stored in the Chemistry library...made me think about if I am looking into the wrong direction(field), but it's better to know more.
After I came back from classes, I read the whole article of "Glow and Behold" by Ian Ashdown, and took notes from it. The last time I read it, I was just scanning through the article, trying to find useful things to put in my abstract. This time, I learned a lot from this article, it's very interesting, I have more ideas about photoluminescence, especially phosphorescence. However, the author also mentioned about the content of the material, which is the chemical part, which is also the part I don't like, because I don't like chemistry, and I never did well in it. The question raised(actually, it raised long time ago): Should I go deeper find out what's inside the materials(samples) and knowing the reason why it's trapping the light and which substances put together would have the best effect? Or I should just perform similar experiments with different conditions, like I stated in the abstract?
If I also go into the chemistry direction, actually, a lot of things have been explained in this article already, and the contents of the materials are mostly known, since most phosphorescent material are made of similar substance. However, it should be intersting....I should think about what I really want to do, and how to make the project not to be boring and too simple....

#### Friday, June 7th, 2002

This morning, I borrowed some books from library: "Luminescence in Chemistry", "Photoluminescence of Solutions" and "Theory and Interpretation of Fluorescence and Phosphorescence". I read a few pages of two of the books, but I haven't quite understood the things mentioned in the books. Maybe I need to read over and over again to get something out of the books.
I read the book "Luminescence in Chemistry", and this book mentioned that phosphorescence is in a triplet-triplet excited state, so that the electrons are trapped in the state, and that's the basic idea about how the light can be stored and emitted even after the excitation source is gone. A long-lived luminescence lifetime is 10^-4 second, and phosphorescence's lifetime is usually longer than that, therefore, it has the ability to emit light after minutes, hours or days.
* Phosphorescence are referred emissions from the phosphors where electrons are slowly released from traps.
* Phosphorescence is radiative transition between states of different multiplicities.
* Fluorescence is reserved for light emitted as result of a transition between states on like multiplicities.

* Triplet-triplet excited states:
1. Trapping electrons(energy is lower)
2. Two electrons with unpaired spin.
3. Return from triplet state to the ground state is forbidden.(Why??)
4. May last 10^3 seconds, which is called "metastable".

#### Monday, June 10th, 2002

* Copy and reorganize the note book to the scientific notebook(I finally have the notebook with me ^_^).
* Continue reading the book "Luminescence in Chemistry", and taking notes on it.
* Going to borrow some more books about phosphorescence in solid state, and the life time of it.
* It turns out the books that I borrowed so far, only the book "Fluorescence and Phophorescence" by Peter Pringsheim is very useful. Hopefully, I can get some other information about phosphorescence in other books, even if they only have a little portion about phosphors.
* Today's work: Went to the libraries trying to find books, and read a little about the chapters that might be useful. Copied the notes I had written on the notebook. I remembered the function I learned in Calculus about growth and decay: Y=Yo*e^kt, as I look into it, , it still leads me to the power law. Therefore, the growth and decay function is not too useful either.

#### Wednesday, June 12th, 2002

I have drawn down some experiment ideas and setups (refer to my lab book), which hopefully would be helpful for later use. I like my ideas very much, but the more important thing to do right now is to learn how to use the equipments, how do the equipments function, what specialties do they have. Also, I should learn more about hyperbolic graphs, and power law graphs. There are so much to learn, and time is so limited, I am a little discouraged on doing the project now. However, I have been trying to convince myself not to be discouraged, but learn more. Hopefully, I will really learn a lot this summer.

#### Thursday, June 13th, 2002

This morning, Dr. Noe gave a talk about some of the equipments that we are going to use in the lab, such as the photodetector, Radio Shack meter, and, the oscilloscope. It's interesting that the lasers have a frequency of 5 kHz, which it produces a barely audible sound, but I didn't hear it. Everyone in the group heard the sound, but I didn't...I guess I have to get my ears checked. We also found out that the computer screen flashes, and blanks for a very tiny fraction of time. It was an interesting talk, and there are so much more than what I wrote here, but I will just go straight to my little discovery now....

I did a little experiment on the light intensity at the first 2 or 3 seconds of samples after it's activated, and the intensity of light source. I assumed that the intensity of light source and the first few seconds on the sample should be the same, but they are not the same. I tested both samples, and did a lot trails, so I assume my experiment is very accurate. I was activating the samples while I measure the light of the lamp at the same time, and hold the detector very close to the sample, so it can reduce the intensity lost over the missing second, and quickly go against the photocell. Taking down the data for both samples over 5 times to take make sure it's accurate. Result is....

The light intensities are different, even if the samples were under the same light source with the photodetector, it can't "trap" as much light as photocell does. because the voltage I detected for the lamp was 12.67 ~ 12.68, while the intensity of the sample B-330 after activated was about 0.80 volts ~ 0.96 volts; and the intensity of the sample B-901 after activated was about 1.028 volts ~ 1.557 volts. Which is about 11.3 volts difference from the lamp and the samples. Therefore, my assumption at the beginning failed was wrong.

Another little note is that the time of activation is relatively important, too, because when I activate the samples for longer time, the intensity is higher, and when I activate the sample for only about 10 seconds, it doesn't have much voltage. Therefore, I assume that the samples contains materials that can only hold a certain amount of electrons, even if the light intensity is very high, and then the electrons emit after all.

* When putting the detector in a distance from the light source, it absorbs less light from it than putting it right against the light bulb.SO, I assume (again) that the photodetector works better, in another words, detects more light when it's held right against the light source in an OPEN area; it should be held in a distance from the light source in a CLOSED reflective surrounding.

#### Friday, June 14th, 2002

I have tried to connect the electronic night light, to measure the the intensity of it, and then I found out(assume) that the electronic night light, which contains similar substance like the samples(I think), doesn't have a afterglow when it's unplugged, besides, it holds less intensity than the stronger sample does. The intensity is about 246.69 mV for the electric night light, but the samples can hold at least 1 volt after it's activate, yet it takes time to decay for the sample.

Why does the sample takes longer time to decay completely?
My assumption is that the electric night light is kept activated by the current when it's plugged, and the substance inside acts like a "tranfer," which let the electron running through and shining, it doesn't hold the light for any second. On the other hand, the samples is not being activated by current, instead it's activated by the light source, in my case, it's the lamp, so it doesn't keep glowing. In addition, we can't see the glow light when the light is still on, while the light is taken away, the intensity decays in the samples. yet because of the electrons are trapped inside, it takes longer time for the sample to emit the light afterward.

Few questions raised:
1.Why does the light light act like a "transfer", instead of acting like a "trap"?
2.If they have similar materials to glow in the dark, why not both taking time to decay?
3.Why can't the electric night light be activated by light, but the current?
4.The electro night light can charge up the samples for a tiny brightness.
***The more questions I have for the comparison, the more I think the electro night light is a fluorescent material.***

I think the night light is a fluorescent material, not a phosphorescent material, even though the light it emits looks like a phosphorescent light with a small amount of light intensity. However, is that true? It's a very interesting question....

#### Monday, June 17th, 2002

I made a very BIG mistake by assuming the electronic Limelite to be a fluorescent or phosphorescent material. It's a electroluminescent material, which emit lights when the electricity comes through; and the light shuts off when the current stopped. The LIMELITE I was working on, electroluminescent material rather then photoluminescent material, but it has a screen which shines like a phosphorescent material. I went on a web page to read about the information of electroluminescence, it's a very simple and helpful, and interesting website, explaining about photonic devices. It also has explanation for optic fibers. The website is actually a visual lab, which interacts with users. It's at Photonic devices
I also learns about different types of detectors, semiconductors, how does a semiconductor work, and etc. There is a lot information of the page, which simplifies the explanation of some terms. It's easier for me to understand the terms I read on other books.

There is one thing which I think it's a little hard for me to learn about things, or communicate with others. Since I spent 4/5 of my life in Taiwan, I learned most things in Chinese, knowing the terms in Chinese, sometimes, it's hard for me when I don't know the vocabulary when people talk about new things, which I know, yet I have no idea about the English term. In addition, it also makes it harder to explain to others about what I know. Of cause there are things that I learned here, and I should be able to explain, but it's a little hard for me to be able to talk in a professional way, which I should, with others. However, I will try to overcome this new found obstacle, which already exist for a long time. Hopefully, I will know more, and gaining more knowledge in a way that I can easily understand.
It was just a little tiny feel about doing research, and trying to find out things I am interested in, yet not knowing too much or not able to comprehend as fast as others. If cause a little frustration comes along, but hopefully, it will get over soon!

As I surf around on the web, I found something interesting in Uselessknowledge.com (which the name of the webpage doesn't sound too convincing) about the often-appeared green emitting light for glow in the dark material. This webpages says that the original emitting light should be pale blue for phosphorescence, but the green light, which is brighter and more stimulating visually, is resulted from "fluorescent dye". By adding different types of fluorescent dye, the color of phosphorescent material can be varied to red, orange, or yellow.

In the afternoon, I spent sometime to set up the equipment for the Limelite intensity v.s. distance. It's a very easy setup, yet I still encountered a few problems.

#### Measurement of Electroluminescent Material-LimeLite

1.Abstract: To measure the light intensity of electroluminescent material at various distances, and compare the result with phosphorescent materials at time decay.

2.Equipments:

• Photodetector.
• A 1 meter meter-stick.
• Limelite(Electroluminescent material used in this measurement).

3.Method: Starting the LimeLite from the position of photocell, measuring the intensity gradually till the intensity is equaled to the background intensity, and record the data.

4.Procedure:

1. Setup the steady position of photodetector, and the meter stick.
2. Measure the background light intensity = 6.7 mV.
3. Initial position reading = 2 cm.
4. Place the LimeLite right in front of the detector to get the initial intensity. Initial Intensity : 183.3 mV.
5. Start to measure the intensity every one centimeter.(refer to the chart in notebook)
6. On the distance column, deduct the 2 cm from each distance to get the actual distance.
7. On the intensity column, deduct the 6.7 mV from each data entry to get the actual intensity from the LimeLite.
8. In addition to the data, at 49 cm, it turns to 7.2 mV; at 58 cm, it turns to 7.1 mV; at 66 cm, it agrees with the background intensity, which is 6.7 mV.
9. Plot the data to the graphing paper.
10. convert and plot the data to log to log scale and semi-log scale to compare.(refer to notebook)

5.Observation: After the LimeLite is positioned at 20 cm(Actual distance from the photodetector is 18 cm), light intensity decreases very slowly, it's about 0.1 ~ 0.2 mV every time it changes. Also, the light intensity appears to be exponential, just like the graph we obtained for the regular phosphor-luminescent samples.

6.Assumption: Electroluminescence has similar property as phosphorescence, that's why they are both decreases are exponentially(????)

7.Comparison:

Phosphorescence:
1. Activated by LIGHT.
2. Light decays exponentially v.s TIME.
3. Afterglow exists.
4. electrons are trapped inside the sample for a period of time.

Electroluminescence:
1. Activated by ELECTRICITY.
2. Light decays exponentially v.s. DISTANCE.
3. No afterglow.
4. Electrons are not trapped inside the substance, they emit immediately after it's excited.

#### Wednesday, June 19th, 2002

I am trying to read about how to program using Qbasic language in DOS format, so I can measure the intensity of eletroluminescent material according to the changing distances without concerning recording the data timely, which is a function existing in the Radio Shack meter. I will also be able to plot the data more precisely using the spreadsheet program.

* Didn't do much about anything today, just reading the book of Crash Course in Qbasic.
* Went to see the metastable state helium lab around the corner, and reminds me to read about the triplet state. Actually, it's very interesting to hear about those things. I will take a closer look at the triplet states and some other relevant topics after my midterm tomorrow.

#### Thursday, June 20th, 2002

After my midterm, I felt more relieved, so I right now till my final comes, I can concentrate more on phosphorescence and all these cool and interesting facts found on the web.
I also put another temporary section of related websites Dr. Noe found at the bottom of this webpage, and I will try to organize all the websites I found which I have read through and I feel it's helpful and understandable, to put on the link of "related website". Also, I will put the websites one by one as I finished reading. I will bring the Qbasic book back, and trying to read more about it, and writing a program tomorrow....hopefully.

#### Friday, June 21, 2002

This morning, I have been reading about the QBASIC book, it's very interesting, because the commands are easy, and since I have learned the C programming language, and Visual Basic language before, I am very used to the commands, and getting the steps very easily. It might also be because I am just reading about the commands that I will need for writing the program to take readings from the meter not by time, but manually. However, a big question if in my head all morning log, that is: How can I convert the data reading RS meter takes to the data in the basic program? How should I connect the RS meter and the program I convert to something I want? I am keeping reading the book, but so far, it doesn't say anything about connecting the QBASIC program with other equipments. I hope I can find it soon. My goal for today is to finish writing a program taking readings from the meter without concerning the time.

I forgot to put other links that Dr. Noe gave to me the other day, I don't think I would be able to read anything about those webpages today.

Another question: Do I want to write a program that record the data directly from the RS meter OR do I want to write a program which just put the data in a array and plot my data in many different possible graphs?

If I want to write a program with only the second type that I mentioned, then what's the difference if I just use the spreadsheet program inside the computer?Therefore, my question is solved....Yet, the first question still hangs around there laughing at me....I better find a way quick to write a program recording the data directly from the Radio Shack meter.

After lunch, Dr. Noe had taught me how to connect the RS meter with the QBasic program to take readings on it. The commands of connecting it to a Basic program are on the owner's manual of the Radio Shack meter. We successfully took readings to the program after experiencing some minor problems. The only thing left is for me to write the whole program out, and insert the commands to be part of my program so it can take readings when I hit some key on the keyboard. I hope I will finish the programming on Monday, so I can take the reading with the RS meter again for a more precise measurements.

The last thing we did was to put my data, which I took by hand, into the spreadsheet program. We plot the data in a log to log scale, and it looks very straight(A very pretty graph, looks like the graph we obtained earlier for the light intensity of phosphorescent sheets.) if we ignore the first few positions( which the intensity drops enormously.) We plot another line according to the hyperbolic formula, which is L(t) = L(o) [b^a/(b+x)^a], where a, b and L(o) control the curvature and the position of the plot. We tried to put in various numbers of the three variables to obtain the best fit-in curve. Besides the straight line part, we also tried to plot the first few positions of the line, to see if that really fits the hyperbolic formula. However, we found out it's hard to fit the first few positions of the curve with the hyperbolic formula. We thought maybe it's not a hyperbolic curve as we thought. On Monday, I should play around with the numbers and to see if there will be any new discovery on this.

#### Monday, June 24th, 2002

Today, I was mainly reading on the webpages about Spin, and trying to find out the definitions of a lot physics-related vocabulary. I learned more about the relations in spins and triplet states. I also learned about what does the symbols mean by J, it's the total angular momentum in the states. Spin means a quantum-mechanical system processes angular momentum,and the angular momentum is always a multiple of h/2, where h indicates Planck's constant, which is 6.26 * 10^-34 J/s. I also read about the eigenvalues that relates to the directions of molecules in spin states, but I don't really understand what that really mean. I have learned eigenvalue and eigenvector in introduction of linear algebra course, but it didn't say anything about how eigenvalues are related to quantum physics. I will read more about it, because I think it will help me to understand more about spin.
There is one question about triplet-singlet states. If I remember correctly, electrons can't go from the triplet state to singlet state, because it's forbidden. However. on the webpage I read, it mentioned that the molecules' energy consists many parts, and the energy stored in triplet states may eventually decay back to the singlet state. Does that mean that electrons can go back to singlet state along with the energy decay?
I read too much physics related webpages and information in one day, so I decided to continue on reading the Qbasic book. I had a little talk with Alex and Owen about programming languages while I was reading the book, and I learned about different types of computer programming language have different usage, and each one of them is better to serve at certain kind of applications.
About my basic programming learning....Well, I am still reading the book, because I have a little problem on how to use the array part. I know it should be easy, but I don't quite understand the dimensional array. Therefore, I was taking my time reading and interpreting between the lines.
The lab is a little busy today, there are a lot people working in the lab today, and I saw the guys taking some of the equipments the hospital donated to their lab. I remember the last time I went to their lab, I was fascinated by the setup. I don't know when will I have enough knowledge to work on physics projects like those physics major do. Hope it will be soon.

#### Tuesday, June 25th, 2002

Today, I was reading about the Qbasic book, because everyone else has to use the computer, I can't keep on reading the webpages. I tried to do a practice program on the computer, but it didn't work, I haven't found out where the bug is, but I will try tomorrow. Sometimes, when I read the program layout, it's like Latin for me; sometimes, it's very easy to understand. I think I need to read more and do more hands on practice on programming; or I think I should just start to write the program. According to my speed writing a C program last semester, I think I need to take about two days to sit there and program and debug...Well...I like programming, just sometimes my logical sense is off...Therefore...it will take more time for me to write a program. I hope this one doesn't take too long, yet can run properly, and be useful.

#### Wednesday, June 26th, 2002

This morning, I was reading on the websites of the students who are working in this lab this summer, too. They all have a very descent, well written, and very organized websites on their project, and they all have a good explanation, and show a depth of their knowledge on their project. Comparing their projects with my own, I feel shamed that I haven't found anything that's quite interesting for people to surf around and go "Oh, this is interesting, and very informative, I should take a deep look on it." I am trying to understand and absorb physics knowledge related to my project, since I barely learned anything deep in this field. I hope I can catch up with other people in this lab faster. I am actually waiting for my summer session 1 to end, because my classes in the afternoon takes too much time for me from the the lab, yet even if I come back from the class, I don't have much time to stay in the lab. I am waiting for summer session 2 to come soon, because by then, I can stay in the lab for a longer time and hopefully I will get more things done in that month. Now that I think about it, the regular REU students have to do a presentation on July 26th, and if I don't have any major work done by then, how can I present? Gee...Time really flies....@_@

In the afternoon, I was basically reading online about the Inverse Square Law, which the formula of it looks like it fits to the graph we obtained on Friday, on the data of intensity v.s. distance on electroluminescent material. The formula for inverse square law is E = I/r^2, where E is the illuminescence, and I is pointance, which the unit is lumen, or steradian candela( Steradian, cd / m^2). To be more precise, the function should be E = I * cos(angle)/ r^2, if considering the angle measurement in the experiment. However, the inverse square law for light is under the condition that assuming the light source is a point source, such as light from the sun, or lights that's coming from beyond the double focus length if a mirror is used as the object. If we assume the point source is the shape of a sphere, the intensity at he surface of the sphere is I = S/(4 * pi * r^2) (where Pi is the value of 3.14159....). If the energy is I at the distance r from the source S, the energy at twice as far from the source is spread over 4 times the area, so the intensity is reduce by a fact of 1/4. For more information,check out the site Inverse Square Law

#### Thursday, June 27th, 2002

I found out what the unit cd/m^2, which is mentioned in Ian Ashdown's Glow and Behold article, means in the luminescent term. It's describe in the link above. Candela per meter square is the standard unit of luminescence. It's the luminous intensity of one candela radiating from a surface whose area is one meter square. What does candela mean? It's defined as the magnitude of an electromagnetic field, in a specific direction, which has a power level of 1/683 watts, which is equivalent to 1.46 * 10 ^ -3 w, per steradian at a frequency of 540 tera-herts(THz), which lies in the range of visible light spectrum.
Also, the unit puzzled me for a while is steradian, which I found out that it's the unit of solid angular measure, that area A of subtended portion of the sphere is r^2, r is the radius of the sphere. You can refer to the graph on Steradian.

I found webpages talking about inverse square law. The formula provided by one of them is exactly the same like what Dr. Noe said: 1/ r^2. It's very interesting, because on the other pages talking about inverse square law, the formula take the Intensity in account, and the angles, too. One difference on this webpage The Inverse Square Law talks about the brightness of the light is proportional to the radius(distance). It shouldn't be any difference, but why is there two different formulas even though they are very similar to each other?
I also found this website describing an experiment that verifies that inverse square law, which is exactly the measurement I did, except for the light source, they used a 60 watts light bulb, and I used the electroluminescent LimeLite. The principle should be the same, despite of the what the light source is.

From the link of Inverse Square Law in Astronomy, I came across this vocabulary of Cephid Variables, which is a class of stars that their brightness is varying over time period. By measuring the variation of the brightness, we know how bright the star really is, and we can also determine how far it is by measuring how bright it appears to be. It's very interesting. Moreover, we can determine the age of the universe by using Cephid Variables. It has a nickname of cosmic yardstick. For more information about it, check out the website inNASA explaining the Cephid Variables. Also check out this website on Cepheid Variables, it talks a little bit about the stars also, and by clicking on the links they provide, there are also stories of stars. If you want to see the graph on how it's related to inverse square law, delta Cephei As you scroll down, you will see the pretty graph they have.

#### Friday, June 28th, 2002

On my page, there is a link of related weblinks, which Dr. Noe just tranfered Peter's page to my page few days ago. I haven't modified the page until this morning, which right now is pretty descent looking and put together the links that I scatterly put on other pages. Now I have put them onto one page, it looks much more descent and well organized(I think). Moreover, it's easier for me to look up reference from it, too. I also added few links and deleted few links that's not useful, I will continue on modify it from now on. Hopefully, it will be a useful page for myself, and people who are trying to look for information on my webpage.

I was searching for reference on the history of phosphorescence, and I found a page on the American Museum of Natural History. It's about the nature of diamonds, and it mentioned that some diamonds have fluorescent qualities, and some have phoshorescent qualities, which they store the high energy of light, and emitting it for a period of time, just like all other phsphorescent materials do. I thought it would be inetersting because they have the pictures of the shines of diamonds under different conditions . However, it's just a comparison of diamonds when the fluorescent light shines on it, and it's regular shine with daylight.

Prof. Metcalf came in today, and he told me that he read over my journal and saw a lot things that I have misunderstanding or confusion about on spin, triplet states, singlet states, and etc. Therefore, he decided to give a talk in the lab, talking about the quantum physics part, so that we can understand the basic of it, and have a idea about what it is. I think it's very nice that he went over the stuff I wrote on my journal, and I know I just wrote everything I did everyday, so the jourmal is a little messy, and not well-organized. However, I think, since it's a journal, I am not really concerned about presenting things that I don't know on the web, because that's what I don't know, and it will remind myself to work on it everyday. For now, since I know that people would read over my page, I will be more careful about what I put on the web, and learn more things everyday, to show some real progress.

#### Monday July 1st, 2002

Today's goal for myself is to write the program out to remeasure the light intensity of the limelite that I used before. I want to have a more precise measurement, so I will be working on it today mainly, and I think Professor Metcalf will give a talk sometime today, I am looking forward to it.

Professor Metcalf's talk was very useful, even thought it was only about the history of the physics, but it helped me to clear out some confusions on the information I wrote in the journal. His talked about the "what's wrong in the clasical physics" today, and he said that there are some mysteries about physics. Ther are some phenomenons that scientists couldn't explain in the 19th century and the early 20th century. I found it very helpful today, the only I was still confused about was the Bohr's statement about he could solve both Rutherford and also the mystery of the dark spots of the sunlight...I think I have to ask Prof. Metcalf to explain from that point on agian tomorrow, because I found that there are so many things he mentioned today were related to my little research on spins and triplet states. So...Things should go smoothly from now on! ^_^

The high school students came, they all look very intellegent, and I think they ARE intellegent. Dr Noe asked us to introduce ourselves like when the high school WISE came, and talking a little about our projects. I felt a little embarassed, I guess I am not confident enough to talk in front of people about what I did, because I still think that I didn't do much on my measurement, and I have to organize my thoughts well on the projects. I mean, when people ask me to describe orally about my projects, I feel shy and not confident, but I can talk a lot when I write on my journal. I guess I need to practice more on public speaking, and maybe take a course like "confidence 101" to build up my confidence.

I am trying to write a program to measure the intensity accoording to the distance using the limelite. I have a little lay out of the source code, but I have problem about storing the data in a file so it can be displayed later on regarding to the distance I input when the measurment is done. However, I am totally stucked in this part. I want to try on the c program first about storing data in a file, I think i forgot how on the C program, so I am lost on the steps right now on programming in the Qbasic...@_@

* Stuff to do tomorrow! Bleaching! why when shining the laswer light to an activated sample, it creates a dark spot on the sample, and it returns to the priginal glow again very soon?

I put in the command that I wrote so far in Qbasic, it's not perfect, but I am just trying to put it in line by line, so I can read more clearly, and easier to debug.So far, I have written down the basic source codes, I guess I won't have too much problems on writing a program taking the reading, but I am thinking about how to out the data in a file, such that when I open the qbasic, it can just read from the data file.

#### Tuesday, July 2nd, 2002

Just like yesterday, Professor Metcalf gave a talk about quantum mechanics this morning. Everything was fine till the horrible wave equation came out with theSchrodinger's explanation. Ironically, this horrible wave equation can solve the mystery about blackbody radiation, mm...I don't know what to say about it now actually.

After the talk, we had some visitors in out lab from the REU physics group. We were basically describing to them about our projects, and I was the second one to describe my project. I felt I am more comfortable today to talk about my project, yet I forgot to mention the most interesting part on my graph that the data appears to be linear when poltting on a log-log scale.

Didn't do much this afternoon, I just simply made my webpages looking prettier using the pictures I like. I am thinking writing a longer "about me" part, but maybe not soon, because I am still thinking about how should I make the meter take readings and convert to a spreadsheet. Today, my mind is full of Qbasic programming, my programs due tomorrow and my CSE113 final next tuesday.

#### Wednesday, July 3rd, 2002

Simply didn't do much today, just attended prof. Metcalf's talk, and understood more about triplet state and singlet state. Hopefully I will get the program done this weekend when I am not studying for my final. I guess I need A LOT luck this time@_@

#### During the July 4th weekend....

I went to a BBQ on July 4th with my suitemates and people from REU mineral physics and geology. It was alright, I don't know most of people there, so I was bored, but they are all nice people, mostly graduate students or junior and seniors in undergraduate.

I ran into my friend, who lived across the hall from me last year, we hung out on Friday in the mall. I guess it's not a good idea to hang out in the mall with friends, because I wanted to buy everything I saw in the mall. @_@ Gotta control my urge of buying clothes....=P

I also created a personal website using one of the webhosting tools, it's not complicated, but it's not done yet, when it's done, I will post it up on the about me link. I also want to create another website on school wegpage which I have requested. I want to start from scratch, type in all the commands that I need. Hopefully I will get it done by the end of the summer.

Othertimes, I was studying for my CSE 113 final. I hope I can get a good grade on it...*Hope Hard*...

#### Monday, July 8th, 2002

I worked on my programming today, which I got the meter taking the reading repeatedly, and recording the distance, too. However, I couldn't get all the data converting to the spreedsheet format when I attempted to read the file from the data. I think I have to work on it.

#### Tuesday, July 9th, 2002

Finally, my first summer session is over, but I don't think my final was too good to pull my grade up too much, but anyway, it's passed.

Yesterday, I have worked on the debugging with Dr. Noe(Actually, Dr. Noe debugged it). Therefore, I cantake a more precised measurement on the limelite, and also it would be helpful for many things as Dr. Noe said (But so far I haven't thought of any good idea to use the program with.) I am going to put my program on the webpage, too. Hopefully it will help people who needs similar program to use. I haven't decided which section I want to put the source code on, but it will be on my page somewhere.

Today I'm exhausted already, but I am going to set up the computer to my little setup for the lime light tomorrow, and work on it. I will also reanalysing the data, and compare the data I will record tomorrow. Hm....Let's call this paragraph of "goals for tomorrow". I will also try to get more information about the inverse aquare law, because I don't think I understand too well on the applications for this law. I would also visit the website Dr. Noe showed me yesterday about the 1 / f, which is the same as the power law. Since I will have more time to be in the lab from now on, I will try to get more things done.

#### Wednesday, July 10th, 2002

I have my setup on the back to work on the limelite reading taking again, but as I was running my program, I found that the program having a little problem on taking readings when there is no distance value entered. I am working on it to it can go back to take the reading while I do the measurement. So far, everything is working, and if I can solve this little tiny problem, it would be perfect for my experiment.

Okay I solved the little problem by adding an IF statement in the loop, so it would test if the distance added in is valid (Not a negative number, and also not no-entry) It's working fine, I got another set of data which I think it would be more precise. However, I found out something tiny about the program that the program doesn't recognize if there is two exactly the same entries. Well, I am not going to worry about it, because I could always convert the data to the spreadsheet format and modify the file to a readable format, and also analyze the data from the spreadsheet.

So I have another set of data, which is mostly looking the same as the one I took by hand. I haven't plug in the dat in the light intensity function yet I don't know what would it come out like. It should be the same because it's not a big difference. I will not spend too much time on this measurement, which is basicly the same one like I did on June 18th.

The next thing I want to do is to use the monochrometer to activate the samples and take readings. Maybe I will see something interesting.

#### Thursday, July 11th, 2002

Alright, so my measurement on limelite is finished today, my program is working well with the RS meter if following the instructions well.(Make a note on the "if") I got few more data and tried to make the background as dark as it can get, but I didn't take the measurement on the background for each readlings separately. The graphs look nice, and I think it fits the inverse square law pretty much, all the floating datas were probably effected by the noises. Therefore, my little project on the limelite is practically done. I have learne how to program with Qbasic program, and I connected the meter and the computer well. Starting tomorrow, I will start on something else, setting up another measurement, and doing as what Dr. Noe suggested to do measurements on the samples, which are activated by sunlight. The only thing I have to concern is the timing that I start the measurement, since I have run from outside to the lab to start the whole thing.

I want to put the graph of limelight on the web, too, and also the coding, but I guess I will just worry about it later, I haven't really thought about how I want to organize my website to a better looking format, and also a easier to find sources. Maybe I will work on it during this weekend.

For the new experiment, as Dr. Noe suggested, I should improve the setup of the equipments...but I think I will worry about it tomorrow, too. I am being lazy now...After a whole day of thinking about why the graph looked ugly before, and also trying to fix little problems in the porgram I wrote to make it a better program....Hm...I need energy supply to stay awake in my class later. @_@

#### Friday, July 12th, 2002

Another week has passed. This week, I was mainly focus on writting the program to take a more precise measurement on LimeLite, but since I already have a nice data on that limelite, I just took another few readings on the limelite to test if the program work well with the RS meter. Like I analyzed earlier, after plotting the data to the graph, it tends to fit the hyperbolic formula. However, it's not 100% fitting into it, the constants should be varied to certain combination that it would fit mostly perfectly. I will do more research on it later, because now, I should work on something new, like activate the samples under sunlihgtm and produce the same experienment like what I did initially.

#### The experiment: LimeLite Intensity Second Run

Abstract and objective are the same as the previous one.
Equipments:
• Meter stick.
• Photodetector.
• RS meter.
• QBasic Program - Trial.bas.
Experiment procedures are the same as the previous one.

1. Initial position is 2cm, uncertainty is 2 mm.
2. Initial background intensity is 0.3 mV, but the uncertainty is about .05 mV, because the accurate reading on the RS meter is 0.1 mV, if the meter reads 0.15, it may be round off to 2 mV, or 1 mV, therefore, when analyzing the data, the uncertainty was taken into account. In general, the reading was precise enough for plotting the intensity..
3. Initial LimeLite intensity is 183.9 mV

observation is the same, I have gotten a very similar yet longer data up to the distance = 100cm.

Only thng left for this program is to try to fit in a proper fuction in it.

#### Qbasic Program - Trial Source Code:

'Program taking reading from RS meter
CLS
PRINT "Distance V.S. Light Intensity Measurement"

OPEN "reading.dat" FOR OUTPUT as #1 'Open(create) file for data recording.
PRINT "Please input a distance value"

Do
Input "Distance="; Dist\$ 'taking reading from keyboard.
IF (dist\$ <= "0") OR (dist\$ = "ent\$") THEN
PRINT "Please give a valid input"
ELSE

OPEN "com2:600, N, 7, 2, RS, CS, DS, CD" FOR RANDOM AS #2
'give the "D" command to activate meter
A\$ = "D"
PRINT #2, A\$
intensity\$ = INPUT\$ (14, #2) 'take reading from meter
close #2
PRINT "Distance = ", dist\$, " ", "Intensity = ", intensity\$
PRINT #1, "Distance = ", dist\$, " ", "Intensity = ", intensity\$
END IF
LOOP UNTIL(dist\$= "999")
'print and store data on screen and print when the file is called
CLOSE #1
'print all data

END

The graph for the data I took with program is to be displayed as followed:

On the graph, the blue line is the data taken from the meter, and the red one is the best fitting line, which we originally thought it should be a hyperbolic function of I(x) = I(0) * (a^2/(a+x)^2), but it turned out to be a variation of the hyperbolic curve, such that the denonimator is not (a + x)^2, but it's (a + x^2). Therefore, the formula of this graph actually fits much better to the function I(x) = I(o) * (a^2/(a+x^2)), or the formula can be written as I(x) = I(0) * (a^2 / ((a + x)^2 - 2ax)) as a functions that's more like hyperbolic function.

Values of parameters:
• a = 1
• x = distance (varies)
• I(o) = 183.9 mV (initial light intensity of LimeLite)

I took out the first reading on the data, because the first data is the intensity of the limelite when it's held right against the photodetector, such that when plotting the graph, it has a enormous change from 0 distance to the first position, which is 1 cm away from the meter, it doesn't fit with the rest of the graph..

#### Monday, July 15th, 2002

Today, I am working on figuring out to to improve the setup on the next measurement that I am going to do with the sample activated by sunlight. Now I know I can use RS meter program to take reading and create a file, but I don't have a complete thought on how to make a setup to take reading right against the photodetector. I am still thinking a best way to make my equipment.

I am also thinking about my presentation on July 26th. I want to do a good presentation using existing datas and file I have, and maybe if I can finish the sunlight experiment and analyze it on time, I can present that, too.

* Had a headache for the passed whole weekend, and still having it now, so my brain is not functionalling too well (when did my brain function normally anyway? O_o). Therefore, I do everything so slowly now. #_#

I have made a black box from paper board, which it's a completely dark environment, and the photodetector positioned facing down. I have tested the light intensity for thw whole blackbox setup, the meter reads 0.00 mV and sometimes -0.01 mV in the black box. There wouldn't be any light leaking in in the black box. The only that has to be controlled is the starting time of data reacording, which I have to work on it....by running up and down stairs to where the measurement takes place to see the approximate time I get to it.

I started the sunlight-activated-sample measurement about 5:05 pm. I activated the sample with sunlight for 2 minutes, and the running time was 45 seconds. Dr. Noe will stop the reading taking in 2 hours, which will be about 7:05 pm. I will then compare the datas between this one and the very first measurement I did tomorrow.
I prefer to take a thorough measurement again tomorrow though, with a actual timing and longer activation time.

9:20 pm, I came back from my class, and I saw thr RS meter is still running. I guess the sunlight is really a better source to activate the sample. However, what cause it to have a longer glowtime, though? what property does the sun have to make the glow last longer? Another question is...Is there a maximum intensity for the sample hold or the sample can hold as much intensity as the sunlight can give...I guess I have to find out.

The meter reading is 1.4 mV now. I don't know if I should terminate the reading, because I was stupid enough to forget to check the initial background light the meter reads before slide the sample under.

I was trying to look for information about the characteristics of an incandescent light and the sunlight. So far, I only learned about that incandescent light is produced by a tungsten filament which glows in a visible light when it has a very high temperature caused by the electricity going through. Hm...Just realized...maybe everyone knows what a incandescent light means except me... By doing research here, I am also learning English a lot. I think it's helpful even though it may appear to look like that I am stupid. It's not I don't know...it's just I don't know the English vocabulary for certain things. Anyway...I guess it's gettinglate, and I am too tired after a whole day of class and working....@_@ I will take another reading, and open another file at 1:00 am and then I will leave it on, maybe I will come back in the early morning to check on it.

#### Tuesday, July 16th, 2002

I am working on analyzing the data I took with the sunlight-activated-sample today. I have several very large files to work on...I guess I won't be able to sleep tonight. Also I have to write out an abstract, too...Hm...I am tired...

#### Wednesday, July 17th, 2002

I have worked on my 6 files of data, which contains thousnads of readings that I took in the 18 hours. I have fixed the bad data, and take the data average over time interval. The time interval I took for averaging the data is for the first 10 seconds, I record the data exactly; for the data between 11 - 100 seconds, I average evrey 10 seconds; for data between 101 - 1001, I took average every 100 seconds, and so on. Every time interval, I took 1/10 of the maximum data number to average to get a best fitting line. Luckly, I got a graph of the averaged data that fits perfectly well to the actual data for each file. I am working on my 4th file of data now. I haven't check on the last file, which contains almost 1 mg of data.... Since it's too big,. I have to break it down to smaller files, and then do the same analysis on the break-down files. Hopefully, I will finish everything by tonight, so I will have time to work on my abstract later on.

I accidentally changed the intensity of one of the data file this morning, so I ended up spanding extra time fixing the file to what it sould be. It was because I forgor to deduct the background light intensity from the readings, and I wanted to subtract the value. As I copied down the cell to the who sheet, I forgot that I didn't have a formula for the intensity, so it ended up to cope the first cell to the whole columnm and it was a straight line on the graph. Therefore, I fixed that file, and still two more files to go...Hope my nearsight doesn't get worse by staring at the computer screen all day long!

Problem raised when I was trying to average the data with a larger interval. The data couldn't possibly show 10000 data in one file since we cut the experiment to several files, one file contains data that belongs to other file as well. Maybe I will try to separate the interval to a smaller one.

I have finished the averaging work on the first 5 files, and I have copied the last file, which is the largest one onto a floppy disk. I will come back tonight and work on the splitting file, and also my abstract. The graphs for the first 5 files look very neat. Since the time interval can't be cut into 10000 intervals because of the data, I used 1000 second intervals to average after 100 seconds, and it worked out very well. I will print them out so I have a sense how the whole graph look like. I will also put them on the web after splitting the files into smaller pieces. and organize it.

#### Thursday, July 18th, 2002

In the morning, the files were splited to t smaller size files, and the smaller files could be imported to the spreadsheet. Basically, what I am doing now is to average the data over a time interval on the spreadsheets again. This wouldn't take too long I think.

I have finished fixing and prganizing and averaging the data over 1000s time interval. So right now I have 10 files of data, and I will be working on my abstract tonight. I will probably coming back from my class later to finish up everything I am doing. I don't think I will get a good analysis on the sunlight-activated-sample graph, but I iwll do my best and thinking of a way to explain it.

#### Friday, July 20th, 2002

I was working on writing my abstract this morning. I think I didn't do a good job on that, though....As always, my writing skill is terrible. I couldn't quite organize my thoughts today...I think it's the weather...Anyway...I will be working on my report as well this weekend, too.

I am thinking about how to write my report, but I don't know how to organize my thought in a way that's coherent and logical...Considering me taking a class about logics for a month...maybe that should help a little. I saw Brendon is writing his report almost to the end...Hm...I have to work on it as well...Hopefully I will write out a descent report without missing anything, or talking about too much detail on some irrelavent things....

#### Monday, July 22nd, 2002

The deadline of abstract is today, so I was rewriting and discussing my abstract with Dr. Noe today for a very long time. I came in the lab about 8:00pm again, because I didn't want to be in my calc 2 class, the instructor is boring, and I took the quiz, which I am confident to get 100 on it. Therefore, I rather to be in the lab working on my abstract than staying in the boring class. Anyway, I have also ploted the modified hyperbolic formula to my very first graph, it fits very well. I have also plotted the averaged data on a new spreadsheet, called sunlight.wq1. I plotted the function of 1/t^n, but I found out the exponent n in this graph is not 1, it's 1.08. I don't know if it's a good or bad result on this measurement. Since there are new things coming out, I guess there will be a little change on my abstract, too. In addition, I still have to prepare my presentation, and a report for the REU talk...Time really flies....

Alright...it's very late now, almost 11:00pm at night, I better get back to my room....so I can wake up early for the Brookhaven trip tomorrow.

#### Tuesday, July 23rd, 2002

It's the Brookhaven trip today, so we didn't come in to the lab until 3:30 pm.
After coming back from BNL, I was working on the spreadsheet to get the graphs to be clearer, and fits better. I found out that if I changed the numbers of constant values a little, I can get a better-fitting graph. For the sunlight measurement, I plug in the fitting line as a function of 1/(a+t^n), where a = 0, and n = 1.21. The exponent is a little bit high. The initial graph, I use the same hyperblic format of formula, and its a value is 1, and the exponent n is .96, which is .04 off from 1. Mm...I haven't discussed with Dr. Noe yet, but data should be fine to present on Thursday.

#### Friday, July 26th, 2002

Today is Friday, but Dr. Noes said that we can have a day off. Its helpful to have this day off, because I was sort of sleepless this passed week. I have been worked on the REU presentation like eveyone else in the lab, and presented on Thursday, July 25th, to the whole summer REU group. I think it was fine, well....I guess it had to be fine, because I even worked till 2:30 am the night before with Jen. It's the latest I have stayed at work for the entire life so far. I guess it's a usual routine for most of scientists to work late, which means I will have to get used to it if I want to be a scientist. Hm...sleep is very important though...tough decision..."To be or not to be, that's the question." (Haha...=P) The presentation went well, even though I was so nervious about, especially my speech, thank God no one asked any tough questions that I didn't know how to answer. First show in Ameriaca...That was good! Quite an experience though =)

I have also put the links up on the web, so people can check out my presentation.

#### Monday, July 29, 2002

Today, the kids are all excited and active (well..maybe they are everyday, just that I didn't notice...=P). I am looking for information about why the sun light can make the phosphorescent sheet decay longer, and I am also thinking about how to take another measurement on the temperature. If using the cup-warmer, I will need a thing to measure the temperatures, too. Well, even after the presentation, there are still a lot of things to do. Hopefully, I will find something new and cool in the next 3 weeks.

The high school intellegent kids were giving a talk and demonstration to their Simon's Fellowship group in the center today. It went well, I think. Hillary's thin film didn't work too well when she was demonstrating. I was trying to help her with it, too. I think it's a very interesting topic that she is doing, and I found out it take the water dripping speed and the concentration of the soap to control the quality of the thin film, it's very interesting. She should make t he thing shorter though, it would be easier for her to add soap on the top.

The bleaching effect is still a mistery for us, and I don't know if Evan is going to do a project on it, but I certainly will look into the reasoning of it. It's very interesting that I thought that stronger sample would show the bleaching effect more, but it was actually the weaker sample, which is the one containing zinc sulfide. In addition, it's more obvious if a red laser is shining on it. I guess it has something to do with the wavelength and the properties of the laser and the phosphorescent sheet. I will look into it if I have time after I figure out the procedure and take another 2 measurements on the samples with the ideas Dr Noe and I came up with.

#### July 31st, 2002

I am trying to figure out how the spreadsheet program works so I can analyze the data faster and more organized. The format of how to average the data is the same as the method I used in the sunlight data, which is to average the data over a time interval. However, this time, I will average the meter reading for every 1/2 of the interval. For example, if I can a 10 second reading, I will average every 5 seconds.

The RS meter program allows data taking for a long time, but the spreadsheet doesn't, it can only hold up to 8000 rows of data. According to the discussion yesterday, we should take the reading every 10 seconds, however, is that necessary to take the reading every 10 seconds or so and then average them again? Will the data analysis be accurate this way?

To adjust the resistance changes the sensitivity of the meter reading, so I guess that's also the reason the sunlight data took a much longer time to decay, because the sensitivity of the meter is higher.

Before trying out the new measurements, I want to have a good setup on the side somehow, so that I can repeat my measurements faster and more accurate. It would be good for my measurement on different activations. The only thing that I am concerning about right now is the decay time of the samples. If the samples take a very long time to decay after activation, and I need 5 different set of measurements, it's going to be time-consuming. I wonder if there is a way to make the samples decaying faster....

The other question Dr. Noe thought about the other day was that what if there is still light in side the sample before it's activation, what effects will it have on the sample? Well, this is a simple question I think. It's only effecting the activation time for the samples. Let's say if the sample takes 2 minutes to activate fully under sunlight, but it will be 1 minute and 30 seconds to activate the sample assuming there is still light trapped inside. Plus, we came to the conclusion that the sample never stops glowing, so there will always be light in the sample, just the amount of light matters.

I was playing with the equipments this afternoon, and trying to make sure everything is working so I can do another set of measurement as soon as possible. I also read about the RS meter user's manual, and how to change the time interval that the meter takes readings. There is a problem about the resistor, it's not a stable resistor that I am using, and I couldn't find any stable resistor for 10 mega ohm resistor. If the resistor problem is sloved and I have gathered the light sources well, I can start my measurement as soon as possible. The light sources that I am thinking about right now would be:

• Incandescent light.
• Fluorescent light.
• blacklight(ultraviolet light).
• Laser light.
• sunlight(which will take a much longer time to decay)

These are the ideas of light source I have so far, I think I will perform the sunlight measurement at the very end, since it's hard for the samples to decay back to ~1 intensity. Since the triplet-singlet state is "forbidden", I guess I will just have to wait for the light decay back for every measurement. Otherwise there won't be any other that I can think of to make the samples decay faster.

Just had a feeling that the hard part of being a scientist is the preparation and the analysis of the experiments. The experiments is the easier part of being a scientist. No wonder why a lot of scientists have white hair even when they are still in their 30 or 40's, because they use too much brain power....(Will I have white hair soon? Haha....hope not...I will try not to think too much then...=P)

#### Thursday, August 1st, 2002

I was working on the resistor part, testing if the resisitance will have a big effect on the sensitivity of the meter. I tested the sensitivity on a unactivated sample for both 10 mega ohm and 1 mega ohm resistor. The meter reads 0.1 mV on the 1 mega ohm while it reads 1.7 to 1.8 mV on the 10 mega ohm, it's about 20 times difference on the intensity of the sample.

My questions comes up again, should I use a smaller resistance for the measurements or should I use a larger one? The benefit of using the larger resistance is that the meter is more sensitive, but it takes much longer time to decay back, and it's the reverse for the 1 mega ohm.
I guess I will use the 1 mega ohm for different light sources measurements, it will take a faster reading; and 10 mega ohm for the longer experiement, which gives more sensitivity.
I was working on making a series connection of the resistors to get the most accurate resistance for 10 mega ohm. It was about .30 mega ohm off from the 10 mega ohm resistance on the sunlight experiment. This time, I am able to make a 9.99 ~ 10.01 mega ohm resistance, which will be a little more accurate on the measurement.

I don't know when is Ken going to be done with the DOS computer, so I can start mine soon....

##### Little thing on the side....
Last night I was talking to my friends online and I sent my webpage to them to read about. As soon as they enter my page, they made comments on the picture on my homepage, which Dr.Noe took for me long time ago. They said: "Jill, change the picture on your homepage, you look so fat on this picture!" I was so upset when I hear this...maybe I should ask Dr. Noe to retake a nice picture for me and change the one on my page now...=(...sigh....

#### Friday, August 2nd, 2002

The high school kids went to the Brookhaven Lab this morning, I guess they had fun there, too.
I talked to Dr. Noe about the resistance, and also the light problem that I have, but yet solved when I came in. I had a misconception on the resistance and the speed of light duration. The resistance doesn't change the speed of light decay. Changing the resistance is only to change the light intensity(the voltage), and the sensitivity of the meter taking readings. Dr. Noe suggested me that I can just stop the meter whenever I want to. I decided to stop the meter at 30 minutes, so the intensity reading will be about 1% of the original reading.

Today, I was working on the setup for the measurement on comparison of the 10 mega ohm resistor, and the 1 mega ohm resistor. It's a sudden idea to do this measurement though, I think it would be interesting to see if the intensity is really 10 times larger. The set up is hard to make this time, because I want to make a mounting base that's stablely holding the limelite, which is attached to a cord. I used tape to tight the photo detector and the limelite with the mounting base, I think if we can get thouse plato toy things to form a mounting base will be much easier and more stable. I will try to go to the mall, and look for it today I guess.

I also did a test run on the 10 mega ohm resistor and 1 mega ohm resistor, I got the readings, but it doesn't look like that the 10 mega ohms one would produce a 10 times larger resistance than the 1 mega ohm resistor. The reading for 10 mega ohm resistor is 0.921 V, and it's 187 mV for the 1 mega ohm resistor. It's kind of strange, but I will work on it later, when I have a more stable setup.

#### Monday, August 5th, 2002

I worked on taking measurements today, I was comparing the intensity on the 10 mega ohm resistor and the 1 mega ohm resistor. I found out something interesting, which I don't understand though. I thought the intensity I detect on the the 10 mega ohm resistor would be 10 times larger than the one on 1 mega ohm, but surprisingly, it's not. It's actually only about 5 times larger than the 1 mega ohm resistor. I calculated, and recalculated, it's still 5 times larger. It happens both on single readings and average readings. I don't know why yet, but in t he mean time, I am taking measurements on the incandescent light with the sample being activated about 5 minutes under light source, and reading will last for 30 minutes. I will do the same measurements with different lights for these few days. I will probably take the longer reading next week.

I recorded the light till the intensity is about 1/10 of the initial light intensity. However, I found out there is a problem with the RS mter program such that it doesn't record from the very first second of the sample. The RS meter program usually flips so many pages because of "OL" message it shows the "OL" message so many times, that when it finally stabllized, the light intensity it record for the first is about 20 seconds later than the activation.

#### Tuesday, August 6th, 2002

I am starting the second measurement on the various-light-sources experiement. The sample was exposed under blacklight for about 5 minutes, and then I take the readings with the RS meter program. Black light is actually a ultraviolet light(UV light), and it has longer wavelength, which is at the the visible end of blue light. Like the measurement I took yesterday, I activate the sample for 5 minutes, and then tuck under the photodetector with a black cover on the top. This measurement will also last for 30 minutes.

The set up for this experiment was described in my earlier journal dates. The variable for this set of measurement is the light source. There are still 2 or 3 more light sources I will have to work with. I will analyze the data later on in the afternoon.

I found out something interesting, the sample is activated very fast with blacklight, it turns to bright shining green emitting light in less then 10 seconds. It may also be that since the black light is a violet color, so it's visible when I activate the light in a dark room, because green and violet lights are not too similar. Yet by using the incandescent light or the fluorescent light, since it brightens up a larger area of the room, the speed of the sample charging up is not that obivious.

Another interesting phenomenon, for little pink alien key chain changed color after it's exposed to the blacklight. The color changes from light pink to dark purplish color. It also emits a very tiny yellowish light. The green alien only emits a very bright green light after it's exposed under the black light, but it doesn't change colors like the pink one. It's very weird, but interesting...I will ask Dr. Noe about it later.

So the little pink alien toy emits light (it fluorescences) when it's exposed to a blacklight, it probably is because it's absorbing some other substance from being exposed to light. The other toy has the same effect, too, but it brightens up, which the light emission is much more visible.

I also did the measurement on fluorescent light, it's very obvious that for the same amount of time of light exposure, the sample doesn't get as much light as other light sources at the initial reading. It might the the reason that the sample was not put directly on the top of the light tube, such that it doesn't get as much light, according to the inverse square law. I will try to see if I can get one light tube down so I can put the sample on top of it.

I decided to add one more light source, which is the sodium light to activate the sample before taking readings. Sodium light is a very strong light, I think it would give the sample more energy, too

#### Wednesday, August 7th, 2002

Tina Shih came to visit, and gave a good talk with the delicious pizzas =) Mm...Yummy! I was working on the measurements again, which I used the sodium light to activate the sample. However, I didn't take the cover off the sodium light, so the light intensity was very little. Therefore, I redo it again with the sodium lamp cover off, and activated the sample for another 5 minutes, and the initial intensity is 300 something mV, and I think it's more reasonable.

I will work on laser light and probably sunlight also tomorrow, if it doesn't rain. So far, the light intensity starts off the best by using the blacklight and the incandescent light. That was Hillary's question when I finished my activation with sodium light.

#### Thursday, August 8th, 2002

Today is the Father's Day in Taiwan!

I am looking for informations about sodium light on the web this morning. I kinda get the idea what's going on in the lamp, but I want to know more about it. I think I should talk to Evan about our projects sometimes, because our projects are very similar. I also think his project is interesting, if he is coming back, I am thinking doing a project with him.

#### Monday, August 12th, 2002

It's the last week of the summer research. I don't think I did much this summer, well...there are still some measurements that I need to take. Towards to the end of this summer, I feel like I am in a rush of doing everything, I have to finish the measurements, and I have to prepare my final, and also moving back home...feeling a little tired...about everything, and I am so lucky that I got a cold now in a hot summer weather....Actually, I don't know how far my project can lead me to.... I talked to my dad and my friends about my project, they all said that it's a very good project that I am doing, and they always gave me suggestions and being very suportive.

A little bit tired, it's probably because of the cold. Even Jen asked me if I am OK when she saw me today, I guess my voice really sounds horrible or something...haha...Just kind of don't understand how a person can catch a cold in the summer.

About the sodium light...Actually, about every kind of light source that I used for my measurements, I don't really understand the difference between each one of them. Incandescent light, sodium light, ultra violet light, sunlight, fluorescent light...as I was doing my measurements, they all did one thing, which is charge up the samples to the sample's maximum strength(I guess)...I haven't done the analysis of different light sources, but I think they should all look the same(similar)....

I will read more information different light sources today...Also trying to find of anyone did similar project as I am doing now.

Back to Home