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A ray of light incident at an angle thet...

A ray of light incident at an angle `theta` on a refracting face of a prism emerges from the other face normally. If the angle of the prism is `5^@` and the prism is made of a material of refractive index 1.5, the angle of incidence is

A

`7.5^@`

B

`5^@`

C

`15^@`

D

`2.5^@`

Text Solution

Verified by Experts

The correct Answer is:
A
Angle of deviation for thin prism is given by,
`delta=(mu-1)A=(1.5-1)xx5^@`
`therefore delta=0.5xx5^@=2.5^@`
Here angle of refraction is `5^@` at the first surface and so from the geometry of figure,

`delta=theta-r`
`therefore theta=delta+r`
`2.5^@+5.0^@`
`7.5^@`
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Knowledge Check

  • The refracting angle of a prism is A and refractive index of the material of the prism is cot(A/2) .The angle of minimum deviation is :

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