A ray of light is incident at small angle I on the surface of prism of small angle A and emerges normally from the oppsite surface. If the refractive index of the material of the prism is mu, the angle of incidence is nearly equal to

Options

A. `(A)/(2mu)`
B. `muA`
C. `(muA)/(2)`
D. `(A)/(mu)`

Answer

B

Explanation

For ray emerges normally `e=0`
Hence `r_(2)=0`
But `A=r_(1)+r_(2)impliesr_(1)=A`
Applying Snell's law at incident face
Refractive index, `mu=(sin i)/(sin r_(1))=(sin i )/(sin A)`
In case of small angle .
`mu=(i)/(A)impliesi=muA`