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Geometrical Optics question

2020 · Q120
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Geometrical Optics question

2020 · Q120

NEETPhysicsGeometrical OpticsMCQ+4 / −1
A ray is incident at an angle of incidence i on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ\muμ, then the angle of incidence is nearly equal to :
  1. A
    2Aμ{{2A} \over \mu }μ2A​
  2. B
    μ\muμA
  3. C
    μA2{{\mu A} \over 2}2μA​
  4. D
    A2μ{A \over {2\mu }}2μA​
View written solutionFree

Correct answer: B

Since the light emerges normally from the other surface, the angle of, emergence

e = 0

For the triangular prism, we know

r1 + r2 = A

But, e = r2 = 0

So, r1 = A

For surface 1,

Snell's Law is sin⁡i=μ.sin⁡r1\sin i = \mu .\sin {r_1}sini=μ.sinr1​

sin⁡i=μ.sin⁡A\sin i = \mu .\sin {A}sini=μ.sinA

For small angles θ\theta θ = sinθ\theta θ

So, i = μ\mu μ.A

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