Refraction Through Triangular Prism

Topic Content:

A ray of light travels in a certain straight line path. After refraction through a glass block, it emerges in a direction parallel to the original direction but slightly displaced to one side. This is called the lateral displacement.

There is no deviation or change in direction of the emergent ray when compared to the incident ray.

Let us now consider the passage of light rays through a glass prism.

• ∠ r = refracting angle
• ∠ i = Incidence Angle
• ∠e = emergence angle
• ∠ D = deviation angle
• ∠ A = angle of the prism
• \( \scriptsize \vec{PQ}\)= incident ray
• \( \scriptsize \vec{QR}\)= refracted ray
• \( \scriptsize \vec{PQ}\)= emergent ray

A ray of light PQ strikes the prism at AB, passes through it and emerges at RS. The deviation of light is due to double refraction at the two sides. If the incident ray is extended forward and the emergent ray is extended backward, they tend to meet at a point O

The angle D formed between the incident and the emergent light is the angle of deviation, and it depends on