Solution:
The crucial angle is influenced by two factors.
(a) The wavelength or colour of light, and
(b) The ambient temperature
Effect on light colour: For a pair of media, the critical angle is lowest for violet light and highest for red light. As a result, the critical angle increases as the wavelength of light increases.
The refractive index of a medium drops as the temperature of the medium rises. As a result, as the temperature rises, the critical angle increases.