Question

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?

• A. ${60}^o$
• B. ${30}^o$
• C. $0^o$
• D. ${90}^o$

Answer 1

The correct option is D ${90}^o$

The angle of refraction for ray is 90 , Imagine now a ray of light travelling from a denser medium to a rarer medium.For example air and water,where water being denser medium and water being rarer.When this ray strikes the interface,its certain that the ray would undergo refraction. The particular value of angle of incidence that the incident ray makes with the normal such that the angle of refraction becomes 90 degree,that is the refracted ray travels parallel to the interface. this particular value of angle of incidence is called critical angle.