Physlet Illustration: Refraction at a Boundary

 

 
n1 = n2 = 
In this simulation, a point source of light lies in a medium with index of refraction n1. The light rays pass into a second medium which has index of refraction n2. Vary the indices of refraction  (1.0 < n < 2.0) and study the behavior of the light rays as they reach the boundary between the two media.

Hints:

  1. If  n1 < n2, how do the various rays refract as they enter the second medium? Which way do they bend? Which rays bend the most?
  2. If you click your mouse at any point on a light ray and then drag the mouse cursor to the right along the ray, you can measure the angle between that ray and the normal to the boundary. Do so for one incident ray and its refracted ray, and verify Snell's law.
  3. If  n1 > n2, how do the various rays refract as they enter the second medium? Which way do they bend? Which rays bend the most?
  4. Make  n1 >> n2, and verify that total internal reflection occurs for some rays. Why does it occur for some rays but not others?
  5. Using the mouse click-and-drag to measure the angles of the incident rays, can you verify the value of the critical angle?

Reference

See Walker, Section 26-5.

Illustration written by Steve Mellema