Define the following terms with respect to a prism,
a) Incident ray b) Normal
c) Angle of incidence d) Emergent ray
e) Angle of emergence f) Angle of the prism
g) Angle of deviation (D).
- Let us consider that APQR represents outline of the prism where it rests on its triangular base.
- Let us assume that a light ray is incident on the plane surface PQ of a prism at M. This ray is called ‘incident ray’. Draw a perpendicular to PQ at M. It becomes a normal to that surface.
- The angle between incident ray and normal is called “angle of incidence” (i).
- The ray is refracted at M. It moves through prism and meets the other plane surface at N and finally comes out of the prism. The ray which comes out of the surface PR at N is called “emergent ray”.
- Draw a perpendicular to PR at point N. The angle between the emergent ray and normal is called angle of emergence
.
- The angle between -the plane surfaces PQ and PR is called the angle of the prism or refracting “angle of prism” (A).
- The angle between the incident ray and emergent ray formed by producing theme backwards is called “angle of deviation” (D).