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

Answer

A

Explanation

As the ray emerges normally from the other face of the prism, therefore, `i_(2) = 0`, therefore, `r_(1) = 0`
As `r_(1) + r_(2) = A`, therefore, `r_(1) = A`
According to Snell's law,
`mu = (sin i_(1))/(sin r_(1)) = (i_(1))/(r_(1))`, when angles are small
`mu = (i)/(A) or i = mu A`