Question

A light ray enters from medium A to medium B as shown in the given Figure .The refractive index of medium B relative to A will be 

(a) greater than unity 

(b) less than unity 

(c) equal to unity

(d) zero

Answer 1

The answer is (b) less than unity

• Here the ray of light bends away from normal when it enters from medium A into medium B.
• This shows that medium B is optically rarer than medium A. 
• Therefore, speed of light in medium B is more than speed of light in medium A. 
• So, ratio of speed of light in medium A to speed of light in medium B will be less than one.