Question

A light ray is travelling from a denser to rarer medium. The angle of incidence is equal to the critical angle. Which of the following statement(s) is/are true?

Note: Question can have mutliple correct options

[2 marks]

• A. The angle of refraction is 90 degrees.
• B. The incident ray bounces back to the denser medium.
• C. The refracted ray passes along the boundary, separating the two mediums.
• D. The incident ray passes undeviated from the denser medium to the rarer medium.

Answer 1

Answer: (A), (C)

The refracted ray passes along the boundary, separating the two mediums.

The critical angle is the angle of incidence in the denser medium corresponding to which the angle of refraction in the rarer medium is 90 degrees. When the angle of incidence in the denser medium is equal to the critical angle, then the refracted ray passes along the boundary, separating the two mediums.

If the angle of incidence is greater than the critical angle, the ray will be reflected back to the same medium without undergoing refraction. This is known as total internal reflection.