Question

(a) A light ray is incident from a denser medium on the boundary separating it from a rarer medium at an angle of incidence equal to the critical angle. What is the angle of refraction for the ray?

(b) Name two factors which affect the critical angle for a given pair of media. State how do the factors affect it.

Answer 1

(a) The angle of refraction becomes 90⁰ when a ray is incident from a denser medium to a rarer medium at an angle of incidence equal to the critical angle.

(b) The two factors which affect the critical angle are

Effect on colour of light: The critical angle for a pair of media is least for the violet light and most for the red light. Thus the critical angle increases with the increase in wavelength of light.

Effect on temperature: On increasing the temperature of medium, its refractive index decreases. So, the critical angle increases with increase in temperature.