Light wave enters from medium 1 to medium 2. Its velocity in `2^(nd)` medium is double from `1^(st)`. For total internal reflection the angle of incidence must be greater than

Options

A. `30^(@)`
B. `60^(@)`
C. `45^(@)`
D. `90^(@)`

Answer

A

Explanation

`(mu_(2))/(mu_(1))=(v_(1))/(v_(2))=(1)/(2)implies(mu_(1))/(mu_(2))=2(mu_(1)gtmu_(2))`
For total internal reflection `._(2)mu_(1)=(1)/(sin C)implies (mu_(1))/(mu_(2))`
`=(1)/(sinC)implies 2=(1)/(sin C)impliesC=30^(@)`
So, for total internal reflection angle of incidence must be greater than `30^(@)`