Name ________________________________________ Period _______________

Critical Angle Worksheet

In each instance, draw a diagram.

1. I can not see the tails of these Orca, even if the water is crystal clear. However, I have no trouble looking down off the side of the boat and seeing a dolphin underwater. Use Physics terms to explain why.

The light rays from the tail of the Orca make a shallow angle with the boundary of the air. This angle is greater than the critical angle, so total internal reflection occurs and the light ray completely reflects back into the water, so you can not see the tail.

The light rays from the dolphin strike the boundary of the air at a much shallower angle to the normal. This angle is less than the critical angle, so you can see the dolphin.

2. Find the critical angle for light traveling from glycerine (n = 1.473) into air.

The formula for critical angle is given on p. 581 of Holt.

You should have memorized that the index of refraction, n, for air is 1.000.

3. Find the critical angle for light traveling from glycerine into water (n = 1.333).

4. Find the critical angle for light traveling from ice (n = 1.309) into air.

5. Which has a smaller critical angle in air, diamond (n = 2.419) or cubic zirconia (n = 2.20)? Show your work.

Diamond:

Cubic Zirconia:

Diamond has a smaller critical angle.

6. Find the sharpest angle that will allow total internal reflection in a fiber optic cable. The glass fiber has an index of refraction of 1.48, and the cladding (material that surrounds the fiber, similar to the insulation of a wire) has an index of refraction n = 1.46.

We are looking for the critical angle. The light is traveling from the fiber to the cladding, so the fiber contains the incident ray, while the cladding contains the refracted ray.