The index of refraction of a certain glass is 1.50.The sine of the critical angle for total internal reflection at a glass-air interface is:
A)0.50
B)0.67
C)0.75
D)1.00
E)1.50

Question

Quizplus · Accepted Answer

The critical angle, θc, is given by θc = sin⁻¹(n2/n1), where n1 and n2 are the indices of refraction of the two mediums in contact (in this case, glass and air).

So, sin θc = sin(sin⁻¹(n2/n1)) = n2/n1.

For total internal reflection to occur, θ > θc, where θ is the angle of incidence. At the critical angle, θ = θc, so we have sin θ = sin θc = n2/n1.

Plugging in n1 = 1 (since we're in air) and n2 = 1.50 (given for the glass), we get sin θc = 0.67. Therefore, the answer is B.

The Index of Refraction of a Certain Glass Is 1