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Question
A light ray of yellow colour is incident on an equilateral glass prism at an angel of incidence equal to 48° and suffers minimum deviation by an angle of 36°.
- What will be the angle of emergence?
- If the angle of incidence is changes to (a) 30°, (b) 60°, state whether the angle of deviation will be equal to, less than or more than 36°?
Solution
We know that, ∠A= r1 + r2 and i + e = A + δ
- In position of minimum deviation ∠i = ∠e = 48° and for equilateral Δ,
∠A= 60°
∵ i + e = A + 8.
e + e = 60 + 36
2e = 96
e = 48° Angle of Emergence -
We are aware that when the incidence angle increases, the deviation angle first decreases and then reaches the minimum value for a particular incidence angle.
- ∠i = 30°, angle of deviation will be greater than 36°
- at ∠i = 60°, angle of deviation will be greater than 36°
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