Question

Explain with diagrams how refraction of incident light takes place from
a) rarer to denser medium [1 Mark]
b) denser to rarer medium (incident angle > critical angle) [1 Mark]
c) denser to rarer medium (incident angle < critical angle) [1 Mark]
d) normal to the surface separating the two media [1 Mark]

Answer 1

a) When light travels from rarer medium to denser medium, the refracted light ray bends towards the normal.
[1 Mark]
b) When the light passes from a denser medium to a rarer medium, the refracted light ray bends away from the normal. When light is incident at an angle higher than the critical angle, then the ray does not refract at all. It completely reflects back to the denser medium which is known as total internal reflection.
[1 Mark]
c) When light travels from a denser medium to a rarer medium at an incident angle less than the critical angle, the ray partially reflected and partially refracted.
[1 Mark]
d) No deviation takes place in the case of a light ray falling normally on a medium i.e., no refraction occurs when the light is incident normally on a boundary between two media.