Question

In the given figure PQ and PR are the two light rays emerging from an object P. The ray PQ is refracted as QS. 

 

1. State the special name given to the angle of incidence ∠PQN of the ray PQ.
2. What is the angle of refraction for the refracted ray QS?
3. Name the phenomenon that occurs if the angle of incidence ∠PQN is increased.
4. The ray PR suffers partial reflection and refraction on the water-air surface. Give reason.
5. Draw in the diagram the refracted ray for the incident ray PR and hence show the position of image of the object P by the letter P’ when seen vertically from above.  

Answer 1

1. ∠PQN Critical angle
   
2. Angle of refraction is 90°.
3. The phenomenon is total internal reflection.

4. Because the ray PR's angle of incidence is smaller than ∠PQN (i.e., the critical angle), the ray PR experiences partial reflection and refraction on the water-air surface.

5.