The light ray in the figure is incident on a glass-air surface. The index of refraction of the glass is 1.74. The approximate critical angle for total internal reflection is

Question

Quizplus · Accepted Answer

Using Snell's Law, we can find the angle of refraction at the glass-air interface:

n1sinθ1 = n2sinθ2

where n1 = index of refraction of incident medium (air), θ1 = angle of incidence, n2 = index of refraction of refractive medium (glass), and θ2 = angle of refraction.

Plugging in the given values, we have:

sinθ2 = (1/1.74)sinθ1

We know that the critical angle is the angle of incidence at which the angle of refraction becomes 90 degrees. So,

sin90° = (1/1.74)sinθc

1 = (1/1.74)sinθc

sinθc = 1.74

θc = sin⁻¹(1.74)

θc ≈ 35°

Therefore, the approximate critical angle for total internal reflection is 35º, which corresponds to choice B.

The Light Ray in the Figure Is Incident on a Glass-Air