Define critical angle

(i) Define critical angle. 

(ii) State one important factor which affects the critical angle of a given medium.

Answer

(i) Critical angle is the angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90°.

(ii) Factors which affects the critical angle:

• Colour
• Wavelength of light and temperature
• Refractive index
• Optical density of the medium
• Nature of the medium
• Speed of light