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

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Answer 1 · 2017-05-08T22:17:18

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

Wikipedia

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#