Question

Refraction does not take place when the angle between the incident light ray and normal to the interface is

• A. 0º
• B. 22·5º
• C. 45º
• D. 60º

Answer 1

The Correct Option is A

Refraction is the bending of light as it passes from one medium to another with a different refractive index. 
This phenomenon is governed by Snell's Law: 
n₁sin(θ₁) = n₂sin(θ₂),
where n₁ and n₂ are the refractive indices of the two media, and θ₁ and θ₂ are the angles of incidence and refraction, respectively.

Refraction does not occur when the angle of incidence (θ₁) is 0º because the light ray travels perpendicular to the interface. In this case, sin(θ₁) is 0, thus according to Snell's Law, sin(θ₂) must also be 0, which means that θ₂ is 0º as well. The light continues in a straight line and does not change direction.

Therefore, refraction does not take place when the angle between the incident light ray and the normal to the interface is 0º.

Answer 2

Concept: Refraction is the bending of light when it passes from one medium to another due to a change in its speed.

However, when the angle of incidence is 0º (i.e., light enters the second medium perpendicularly to the surface), there is no bending of light. The light ray passes straight through, and refraction does not appear to take place, although its speed still changes. 

Correct Answer: 0º