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Question
Explain briefly, with the help of a neat labelled diagram, how white light gets dispersed by a prism. On which surface of a prism, there is both dispersion and deviation of light, and on which surface of the prism, there is only deviation of light ?
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Solution
When white light is incident on the first surface of a prism and enters in glass, light of different colours due to different speeds in glass, is refracted or deviated through different angles. Thus the dispersion of white light into its constituent colours takes place at the first surface of prism.
On the second surface, only refraction takes place and different colours are deviated through different angles. As a result, the colours get further separated on refraction at the second surface (violet being deviated the most and red the least).
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RELATED QUESTIONS
After tracing the path of a ray of light through a glass prism a student marked the angle of incidence (∠i), angle of refraction (∠r) angle of emergence (∠e) and the angle of deviation (∠D) as shown in the diagram. The correctly marked angles are :
(A) ∠i and ∠r
(B) ∠i and ∠e
(C) ∠i, ∠e and ∠D
(D) ∠i, ∠r and ∠e
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