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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.
- State the special name given to the angle of incidence ∠PQN of the ray PQ.
- What is the angle of refraction for the refracted ray QS?
- Name the phenomenon that occurs if the angle of incidence ∠PQN is increased.
- The ray PR suffers partial reflection and refraction on the water-air surface. Give reason.
- 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.
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Solution
- ∠PQN Critical angle
- Angle of refraction is 90°.
- The phenomenon is total internal reflection.
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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.
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