Notes for Refraction of light through a triangular glass prism - Class 10 Science Chapter 10 The Human Eye and the Colourful World is prepared by our senior and renowned teachers of Param Himalaya
What is Prism:
triangular glass prism has two triangular bases and three rectangular lateral surfaces. These surfaces are inclined to each other. The angle between its two lateral faces is called the angle of the prism.
Reason behind Bending of light Through prism :
As per Snell’s law, light travelling from a rarer medium to a denser medium bends towards the normal, and vice versa. Glass is denser than air, and thus, when a ray of light falls on the surface of the prism, it bends towards the normal. According to the diagram, ray PE falls on the surface of the prism and bends towards the normal NE. Then, while moving from the glass to the air, the emergent ray FS bends away from the normal MF.
What is Angle of deviation (D):
The angle between the direction of incident ray and the emergent ray, is called the angle of deviation.
Relation of all the four angles ∠A, ∠D, ∠i and ∠e. :
∠A +∠D = ∠i + ∠e
Angle of deviation depends upon the:
(a) angle of prism.
(b) nature of material of the prism.
(c) angle of incidence.
When angle of incidence increases, angle of deviation decreases, till it becomes minimum at a particular angle of incidence.
The refracted ray becomes parallel to the base of the prism under the minimum deviation position.