Wednesday, Feb 25, 2009

Collected RA 18.1

Talked about reflection and refraction.
Reflection - for specular reflection, angle of incidence = angle of reflection. Defined the normal. Did problem of viewing self in mirror - how much mirror do you need. Demo of how much of you you can see vs how far away you are.

Mentioned diffuse reflection.

Refraction - Bending of a wave as it goes from one medium into another in which it travels at a different speed. Demo in hallway using people wave.
Sketched pictures of the demo on the board defining wave front and ray. Show that when going from fast to slow, the ray bends towards the normal.

Introduced Snell's Law - n1 * sin(theta1) = n2 * sin(theta2)
n is the index of refraction. For light n = c/v

For other waves, sin(theta1)/v1 = sin(theta2)/v2

Students did lab on measuring the speed of sound using the tube.
Lab write-up due Friday: Include Name, Partners, Date, Name of Lab
Brief description of lab, data table, measured speed of sound.
Calculate the the accepted value and compare measured to accepted for that temperature.

Students also did the Snell's Law lab in which they measured the index of refraction of water using the semi-circular containers. Students measured the angles of incidence and refraction and then used the laptops with Excel to make a data table and plot sin(angle of incidence)/sin (angle of refraction). The slope gave the index of refraction of water assuming the index of refraction in air is 1.
Write-up: Name, Partners, Date, Name of Lab
Brief description of lab, data table, graph from Excel, Conclusion.

Both lab write-ups are due on Friday