# Find the Angle of Deviation. - Physics

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.

#### Solution

The angle of deviation δ for a ray of light in a prism is given by

δ=i+eA

where
= Angle of incidence of ray
= Its angle of emergence
= 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

Concept: Dispersion by a Prism
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