A ray of light travels from a denser to a rarer medium. After refraction, it
bends away from the normal. When we keep
increasing the angle of incidence, the angle of refraction also increases till the refracted ray gazes
along the interface of two media.The angle of incidence for which it happens is called critical angle.If the angle of incidence is increased further the ray
wil not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light.

(i)The critical angle for a pair of two media A and B of refractive indices
2.0 and 1.0 respectively is
(a) 0°
(b) 30°
(c) 45°
(d) 60°

(ii) The critical angle of pair of a medium and air is 30°. The speed of
light in the medium is:

(a) 1x 10⁸ m s^-1
(b) 1.5 x 10⁸ m s^-1
(c) 2.2x 10⁸ m s^-1
(d) 2.8 x10 m s^-1