Wednesday, July 9, 2014

Bending light

Today physics class began with Mary lecturing on impulse and momentum. She also explained that force and time are inversely related, so in collisions, the longer it takes to stop the less force is exerted on you. Then she talked about conservation of momentum and conservation of energy, and she talked about some of the most common types of energy, like gravitational potential, elastic, kinetic, and heat, as well as the differences between mechanical energy and non-mechanical energy. (Mechanical energy has to do with the ability of an object to move--kinetic, potential, etc. Non-mechanical is based on the motion of the molecules of an object--for example, thermal energy.)

A transverse wave
Then we did a short lab about bouncing balls and measuring the different types of energy the ball has in order to see the relationships between the types of energy. After the lab, Bill gave a presentation on waves, in particular waves of light and sound. He told us about the differences between transverse waves (like light waves and ocean waves) as opposed to longitudinal waves like sound, where the air is compressed and then released. He used cleverly constructed wave machines to show us clearly how each worked.

Bill explaining waves
Then, after lunch, Bill told us more about light waves and how they can interfere with themselves, which related to our lab. We aimed lasers through tiny slits (on the order of tens of nanometers) and measured the resulting patterns to find the wavelength of light. Given that we were measuring with meter sticks in a dark room, we were surprisingly accurate. My group finished our lab early (3:10!) and so we were able to leave class very early. 

Walking back from dinner, Donna and I saw Ben Franklin looking forward to his pizza dinner. After dinner, we had meetings with our RCs and had to decide what activities we wanted to do in the next few days. Tomorrow my RC group will be going out to dinner and then getting ice cream, and on Friday we'll be seeing a movie.

A beautiful tree in the quad

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