Homework #4 Refraction
Equations for this homework assignment:
Snell's Law: n1sinq1 = n2sinq2

Critical angle: sinqc = n2 /n1


Please answer all questions completely. If calculations are required, show enough steps so that I can follow your reasoning.

1. Define:

a) critical angle

b) total internal reflection

c) dispersion

2. A ray of green light (550 nm) enters a block of salt. From the table on page 6, the index of refraction of table salt is 1.53

a) What is the wavelength of the light inside the block of salt?

b) What is the speed of light inside the block of salt?

 3. A beam of light is incident on a flat piece of plastic at an incident angle of 45o. The angle of refraction is measured to be 26.5o

a. What is the index of refraction of the material?
b. From the table on page 6 of the notes, what might this material be?

4. A ray of light strikes the interface between air and water at a 20o angle. The ray is partly reflected by Fresnel reflection (Law of reflection) and partly refracted (Snell's law). (Note that in the other problems, there was also a reflected ray, but you weren't asked to show it, or to even consider it!)

a. What is the angle of reflection (back into the air)?
b. What is the angle of refraction in the water?

5. What is the critical angle for light going from diamond into air? Compare your answer to the example on page 12 for light going from water into air. This small critical angle accounts for the "sparkle" of a properly faceted diamond.