Refraction of Light at Plane Surfaces — Physics STD 10 — Question

The factors which affect the critical angle are:
(i) The colour (or wavelength) of light, and
(ii) The temperature
(i) Effect of colour of light: The critical angle for a pair of media is less for the violet light and more for the red light. Thus critical angle increases with increase in wavelength of light.
(ii) Effect of temperature: The critical angle increases with increase in temperature because on increasing the temperature of medium, its refractive index decreases.