Light is incident from glass `(mu = 1.50)` to water `(mu = 1.33)` find the range of the angle of deviation for which there are two angles of incidence.

Answer

A, C

Explanation

`mu_g = 1.5 = (3)/(2), mu_w = 1.33 = (4)/(3)`
For two angles of incidence,
1. When light passes straight through Normal,
`rArr Angle of incidence = 0^@`
`rArr Angle of refraction = 0^@`
`rArr Angle of deviation = 0^@`
2. When light is incident at critical angle,
`(sinC)/(sin r) = (mu_0)/(mu_g)`
(since light passing from glass to water)
`rArr sin C = (8)/(9)`
`rArr C = sin^(-1) ((8)/(9)) = 62.73^@`
`rArr Angle of devision
`=990^@ - C`
`=90 - sin^(-1)(8)/(9)`
`= cos^(-1) (8)/(9)`
`=37.27^@`
Here, if the angle of increased beyoned critical angle, total internal reflaction occurs and deviation decreases. So the range of deviation is `0 to cos ^(-1)((8)/(9))`