Question

A light beam is incident at an angle twice the angle of refraction. The angle of refraction is ______. 

Options

• `2 cos ^-1 (µ/2)`

• `cos ^-1 (2µ)`

• `1/2 cos ^-1 (µ/2)`

• `cos ^-1 (µ/2)`

Answer 1

A light beam is incident at an angle twice the angle of refraction. The angle of refraction is `cos ^-1 (µ/2)`

Explanation:

i= 2r

`sin i/sin r= µ`

`(sin2r)/sin r= µ`

`(2sinrcosr)/sin r= µ`

∴ `cosr= µ/2 ⇒ r= cos ^-1 ( µ/2)`