Question

Which statement is true about the critical angle of a medium with respect to air? The refractive index of the medium is taken with respect to air.
A. The critical angle increases as the refractive index increases.
B. The critical angle decreases as the refractive index decreases.
C. The critical angle does not change when there is a change in the refractive index.
D. The critical angle is equal to the refractive index.

Answer 1

The correct option is D.
The critical angle is defined as the angle of incidence, which provides an angle of refraction of 90 degree. At any angle of incidence greater than the critical angle, all the light will totally reflected, resulting in total internal reflection.Thus, the critical angle is equal to the refractive index.