# Journal

### 3 August 2006

Laser Sam is here for today. He showed me how to align a front mirror of a laser. Now I know how sensitive the lasers mirrors are. if you are off by a fraction of a millimeter, the laser will not lase. Originally we aligned the mirror independent of the lasers housing. This proved to be very ineffective since the slightest tap of the laser would unalign the mirror. This morning I realigned the mirror so that it is mounted on the lasers housing. now you can move the laser as one and it will continue to lase unless someone physically unaligns the mirror. Sam is a very cool guy and i look forward to working with him and learning from him in the hours to come.

### 31 July 2006

I just got back from a talk about fiber lasers. The applications of these lasers is the same as that of conventional lasers; but their efficiency far surpasses that of conventional lasers. Anyway, back to the project. I have the Snell's Law Method set up and ready to go, I just need to work out the math a little more. There is an interesting application for my prior experiment that Maaneli and I figured out. If you take a gradient index of refraction and set it up such that it is in a spherical shape, you can model the way light behaves around a gravitational field. Furthermore, if you have a GRIN that goes to infinity, you can model black holes. I am very happy to see the astrophysical applications that my research has, and greatly look forward to pursuing those implications in the future.

### 24 July 2006

I Learned a lot about the necessities for recording things accurately. I also learned that everything is not always what it seems to be. When I did the calculations for Brewster's angle between air and glass, it was something much different than what I had originally found in my experiment. It was only a difference of one degree. I measured 57.3 degrees, and calculated 56.3 degrees. I figured oh, it's only one degree, it is probably a miss-measurement. However, using the calculated number, I was getting an index that was way off; greater than that of glass. So I figured that the material that the fish tank is made out of is not glass but is in fact some type of plastic. Using the Brewster's angle I measured, I calculated a much different index. Then I applied that index and the measured Brewster's angle; Ta-Dah the formula works. I correctly calculated the index of water, and corn syrup. Now that Dr. Noe has gotten me the supplies I need for the Snell's Law method I will get to work on that as soon as possible.

### 17 July 2006

Now that I have finished the "displacement method" it is time to go to a new level and measure a variant index of refraction. This uses Fresnel Equations. Instead of looking at the distance that the laser is offset by a medium, I will observe the relative intensities of the two reflections of the laser of the glass. Using Fresnel's Equations and the data I record from my experiment I will be able to measure the Index of Refraction of virtually any medium inside the fish tank.

### 12 July 2006

Recap on the beginnings of the Mini-Project: The first set of data points that i measured was best-fit to n=1.4. Since the accepted index of refraction for water is 1.33, i knew something was off. Dr. Noe suggested that i use graph paper, or remake the angles more carefully. Using a piece of graph paper instead of a marker in the plexy-glass made my measurements much more accurate and easy to read. The first set of data did not fit to the accepted index value for water. I learned through this activity that it is very easy to make errors by approximating the position of a laser beam. To get an accurate reading you must try to be as accurate as the laser is that you are reading.

### 06 July 2006

HELLO WORLD! First journal entry, here goes. Today I worked with the laser pointers and the fish tank; not a hard project but one to 'get my feet wet'. I learned that there are many ways to measure the Index Of Refraction of water using different laws and geometric properties. Thinking about the different ways to measure the IOR really made me realize how some processes would be easier and others harder. I will put links up about the different ways of measuring IOR as i find them.

 Astro MattJune 2006 Home  Laser Teaching Center