Week 7:

July 15, 2002 - July 19, 2002

This is the beginning of the seventh week. I have to start thinking about what I am going to do for my presentation. I am planning on also filling up another fishtank so that I can see how it changes with time. I also want to be able to do comparisons with how pure corn syrup might vary as compared to say water. That way these rotation values that I measured can be compared. I plan to make out a chart of all of this.

Today I also received the semicircular glass disk that I wanted to use with my fishtank. With this I am hoping that this way I will be able to eliminate refraction at the initial interface such as I discussed earlier.

On Tuesday, I went to a lunch with Professor Graf and everybody else who is a part of the REU Physics program. This is the last week for me to work on whatever I will be presenting on Thursday. I will have to have an abstract completed on Monday. This will not be the end of my research however. I plan to continue with my project for an aditional three weeks.

For this week however, I have set out all of my important goals. I would like to hae a few graphs of data. Today I have been spending some of my time working on calibrating the laser. Whenever I shone the laser through the tank, I would measure the height that the laser pointer enters the tank and the height that it exits the tank. This gives me an idea of how steep the curve is as it is passing through the tank. Generally, I have noticed that as you approach the bottom of the tank the laser pointer will curve more. In fact the change in height will get so great that at the very bottom the laser pointer does not visually exit the bottom of the tank because there is not enough room. So there is a certain limit to how much of the tank that I can measure. I will have to develop another way to be able to measure the very bottom of the tank. Perhaps a method involving total internal reflection would be best because then the laser beam would not have to pass through the other end of the tank. It will still measure the index at that point but it will not need to transmit it through all of the media in order to do this. Be able to achieve this would be a great addition of data for my project.

There are a lot of things that I have left to do this week in the lab.

Some of my weekly goals:

1. Measure and graph out all the data that I collect.

2. Graph out previous ones and discuss any changes from a weekend of sitting. Also the fact that as more time passes the water is evaporating and this means that I should be observing an increase in index of refraction.

3. I have to measure the rotation for pure corn syrup and also for a 50/50 "corn syrup and water" solution. These rotation values will give me something for a comparison so that I can translate the rotation vlaues that I measured into index refraction measurements. I can place the "corn syrup and water" solution into the prism to measure its index of refraction. This will give me a value because I am not sure if I can find a measurement for this value online.

I graphed out one of my trials. In the end I am noticing that through a decrease in height the rotation continually increases. At first some predictions were made that there might be some dips. But in my measurements I have not noticed any.

Observations that I have made for more accurate mesasurements:

We all know that in science it is very important to learn to make accurate measurements. I enjoy working on this project because I feel it gives me a good practice for this important skill of science. If data is going to be collected it is vital for it to be accurate. Or else its use will not be the same.

An important note that needs to be made is that first the rotation should be done before the measurements are made. Because the laser will move around a little bit when it is rotated.

Using the polarization is not the only method that I plan to use with measuring the index of refraction in my tank. I also got a hold of the semicircular piece of glass that I want to use.

I tried to use the semicircular piece of glass but it was not successful. I had trouble mounting it to the front of the tank. The laser beam has to pass through the center of the glass in order for it to not interact through the air/glass interface.

Keeping the piece mounted through the tank without supporting it through its center is a difficult feat. Without it being perfectly perpendicular to the tank the measurements would not be as accurate. The error margin would be difficult to calculate as well.

Although I planned to fill up another tank in the end I have not yet. I did receive some extra corn syrup bottles. I poured out one of the bottles into a glass beaker. I used to same method of polarizing the laser light through the corn syrup bottle. I made sure that first I calibrated the rotation of the laser against the value of 0 being the polarization of the laser through the air. This is because polarization of the laser light through air would be the same as water. Now I had the rotation value for corn syrup. All that is left to be done is to devise a formula on relating these things.