Question

# A ray of monochromatic light is incident on one refracting face of a prism of angle . It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of the prism is , the angle of incidence on the first face of the prism is :

A
B
C
D
Medium
Solution
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Correct option is B)

## The correct option is BHint: Consider snells law and Critical angleCritical angle is given as,Where, is the refractive index. In order to describe the relation between the angle of incidence and reflection snells law is used.Where is the angle of incidence and is the angle of reflection.Explanation for correct answer:Step 1: Information requiredCritical angle is given as,Where, is the refractive index.In order to describe the relation between the angle of incidence and reflection snells law is used.Here, is angle of incidence  is the angle of reflection.Angle of prism  Refractive index  Step 2: Calculate the angle of reflection,The angle of the prism is the sum of reflection and critical angle.Then,Substitute the value of critical angle and angle of prism in the above equation So, the angle of reflection is .Step 3: Calculate angle of incidence,Consider snells law,Hence the angle of incidence is .

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