Light is incident from a medium into air at two possible angles of incidence (A) 20^ and (B) 40^ . In the medium light travels 3.0 ~cm in 0.2 ~ns . The ray will :

Step-by-step solution

Velocity of light in medium V _ med = 3 ~cm 0.2 ~ns = 3 10⁻² ~m 0.2 10⁻⁹ ~s =1.5 ~m / s Refractive index of the medium = V_ air V_ med = 3 10^8 1.5 =2 ~m / s As = 1 C C = 1 = 1 2 =30^ Condition of TIR is angle of incidence i must be greater than critical angle. Hence ray will suffer TIR in case of (B) (i=40^ >30^ ) only.