A ray is incident from a medium of refractive index 2 into a medium of refractive index 1 . The critical angle is

Step-by-step solution

Critical angle is defined as the angle of incidence, when light is travelling from denser medium to rarer medium, at which the angle of refraction is 90 ° . Therefore, i c = sin - 1 μ 2 μ 1 = sin - 1 1 2 = 30 °