Question

The critical angle for glass is $42°$. The corresponding angle of refraction is:

• A. $0°$
• B. $90°$
• C. lesser than $90°$ but more than $42°$
• D. no angle of refraction

Answer 1

The correct option is B

$90°$

The explanation for correct option:

• Critical angle: Angle of incidence in a denser medium, for which the angle of refraction in the rarer medium is $90°$ is called the critical angle.
• So option (a), $90°$ is the correct choice.

The explanation for incorrect option:

• Option (a) The angle of refraction is $90°$, so angle of refraction can't be $0°$. It is an incorrect choice.
• Option (c) The angle of refraction is exactly equal to $90°$ neither lesser than $90°$ nore more than $42°$. So this is an incorrect choice.
• Option (d) As the angle of refraction is $90°$, so this cannot be true.

Hence, the correct choice is an option (a), $90°$ .