Question

A ray is incident at an angle of incidence on one surface of a prism of small angle and emerges normally from the opposite surface. If the refractive index of the material of the prism is , the angle of incidence is nearly equal to :

A

B

C

D

Medium
Updated on : 2022-09-05
Solution
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Correct option is D)

Hint: Here, we have to apply the concept of angle of deviation

Solution:

Step1: Draw free body diagram

 

 

Step2: Apply given conditions

According to free body diagram,

i=Angle of incident, A=Small angle of prism & µ=Refractive index of material
Assume, e= angle of emergence
given that, the incident ray
emerges normally from the opposite surface,

Hence,
Step3: Find angle of deviation

We know the angle of deviation () can be,


In case of prism, we know that, sum of small angle of prism & angle of deviation in a prism is equal to the sum of angle of incidence and angle of emergence. So, we get,

Submit values from equation (1) & (2) in equation (3) we get,

or
Hence, option (D) is correct.

 

 

 

 

 

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