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Question
A ray of light passes through an equilateral glass prism such that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of angle of prism. Find the angle of deviation.
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Solution
The angle of deviation δ for a ray of light in a prism is given by
δ=i+e−A
where
i = Angle of incidence of ray
e = Its angle of emergence
A = Angle of prism
`∵e=i`
` ⇒δ=2i−A`
Given:` i=e=3/4A`
`∴δ=2×3/4A−A`
`⇒δ=1/2A`
As the prism is equailateral,⇒A=60°
`∴δ=12×60°`
`⇒δ=30`
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