# Research Journal

## October 2011

I haven't updated on my project for some time, as I've been really busy with my other classes for the last few weeks. I have been reading a lot about film and digital photography, and pros and cons of both. I recently interacted with Prof. Pascuzzi [my PHY 132 teacher] regarding the same, as apart from being a professor, he is a professional photographer. I have compiled some notes and ideas on the physical phenomena of depth of field and thermal noise in pictures. I am currently studying about the focus bracket optimization for appropriate depth of field and the ISO settings of a digital camera. This wikipedia article has a very thorough discussion of depth-of-field.

## September 2011

First day at the Laser Center: Dr. Noe gave me an overview about some of his students' complete and ongoing projects at the LASER Center. He demonstrated the mirage toy: a set up with an arrangement of two curved mirrors and small plastic pigs whose image appears to be real on top of the mirrors. A laser beam, when shined upon this image, retraces its path back onto the actual pigs. He asked me to figure out the quadratic equation dealing with the focal length formula relating image and object distances. I tried to describe different cases of the discriminant of the quadratic equation in relation to the magnification and focal length. We talked a little about the Hemite polynomials, which I want to learn more about. Something I found interesting was the experiment with square arrangement of lenses which led to diffraction pattern, and even a slight pull of the lens through a rubber band could cause a large scale deviation in the diffraction pattern and change in wavelengths. He showed me the experiment consisting of the tuning forks and wind column, demonstrating when the waves are in phase and out of phase, and beats.

The next day, I had a startling conversation with Dr. Noe. He asked me what "LASER" stood for. I knew that it was lying in some corner of my brain, but I just couldn't recall, even though I had been visiting the Laser Center quite often! After a brainstorm, I tallied and committed it to memory: Light Amplification by Stimulated Emission of Radiation.

Dr. Noe told me a lot of interesting facts about the Red-Eye Effect (green in case of animals), which occurs in photographs taken with flash. The surface of the retina in a human eye is consists of spherical particles. When light rays are incident on these particles, they get reflected in the same direction from which they entered. Hence, when the flash is switched on, the light coming from the camera retraces its path and our eyes appear like red blobs due to the presence of internal structure and arrangement of cells and blood vessels at the back of the retina. The same effect can be observed in cats and dogs, but with green blobs due to a different slightly biology of their retina.

Something I found interesting was the interference pattern of the light in an inferometer set up, with mirrors kept in a sqaure arrangement. I noticed how even a tiny shift one of the mirrors (by slight retraction of a rubber-band) could result in significant movement of the fringe-pattern.