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ICSE Class 10 Physics Question 20 of 27

Solved Sample Paper 2 — Question 5

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5
Question

Question 5(ii)

(a) What are the necessary conditions for TIR?

(b) Draw a diagram to show how rays of light are totally reflected when fall normally on the face of a right angled prism. Where is this action of prism used?

Answer

(a) The two necessary conditions for total internal reflection are :

  1. The light must travel from a denser medium to a rarer medium.
  2. The angle of incidence must be greater than the critical angle for the pair of media.

(b) Below ray diagram shows the total internal reflection of light rays falling normally on the face of a right angled prism:

Draw a diagram to show how rays of light are totally reflected when fall normally on the face of a right angled prism. Where is this action of prism used? Physics Sample Paper Solved ICSE Class 10.

This action of prism is used in a periscope where a total reflecting prism is preferred over a plane mirror.