Week 3 Lecture 4
Solutions at the bottom.

1)  In-video quiz at timepoint 02:48.

"In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions."

Wikipedia - diffraction grating, http://en.wikipedia.org/wiki/Diffraction_grating

2)  In-video quiz at timepoint 07:02.

Light can also be affected by the Doppler effect.  If you were to drive your car extremely fast (close to the speed of light) toward a green traffic light in an effort to make it before it changes, which color below might the traffic light appear to you as you approach it?

A) Blue
B) Yellow
C) Orange
D) Red

Solutions:

2) The correct answer is: A) Blue

As you approach a light source (or a light source approaches you) the wavelength you observe shortens and the frequency you observe increases.  Visible light ranges from shorter wavelength violet light through blue, green, yellow, and orange to longer wavelength red light.  Thus the green light from the traffic signal will become blue or violet, but not yellow, orange or red.