Question

Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence define the angle of deviation.

Answer 1

Here PE is the incident ray, EF is the refracted ray and FS is the emergent ray. A ray of light is entering from air to glass at the first surface AB. The light ray on refraction has bent towards the normal. At the second surface AC, the light ray has entered from glass to air. Hence it has bent away from normal. The specific shape of the prism makes the emergent ray bend at an angle to the direction of the incident ray. This angle is called the angle of deviation. In this case ∠D is the angle of deviation. The angle between the incident ray and emergent ray is called angle of deviation.

PE = Incident Ray

EF = Refracted ray

FS = Emergent ray

∠A = Angle of the prism

∠i = Angle of incidence

∠r = Angle of refraction

∠e = Angle of emergence

∠D = Angle of deviation