Question

The critical angle for total internal reflection in lucite is 41 degrees. How do you find lucite's index of refraction?

Answer 1

This picture shows the crossover point between refraction and reflection (from medium to less dense medium).

In terms of Snell's Law:

`n_1 sin theta_1=n_2 sin theta _2`

But at the critical angle, `theta_c`, we have:

`n_1 sin theta_c =1 * sin (pi/2) [= 1]`

`implies n_1 = 1/sin( 41^o) = 1.524`

NB: Total internal reflection can only occur if `n_1 > n_2`