Physics
A light ray is incident from a denser medium on the boundary separating it from a rarer medium at an angle of incidence equal to the critical angle. What is the angle of refraction for the ray?
Answer
The angle of refraction becomes equal to 90° when a light ray is incident from a denser medium on the boundary separating it from a rarer medium at an angle of incidence equal to the critical angle. Below diagram shows the path of the ray when angle of incidence is equal to the critical angle:

Related Questions
How is the critical angle related to the refractive index of a medium?
State the approximate value of the critical angle for
(a) glass-air surface
(b) water-air surface.
The critical angle for glass-air is 45° for the light of yellow colour. State whether it will be less than, equal to, or more than 45° for
(i) red light,
(ii) blue light ?
Which colour of light has higher critical angle ? Red light or green light.