Question

The path of a ray of light passing through a glass prism is shown below:

In this diagram the angle of prism, angle of incidence, angle of emergence and angle of deviation respectively have been represented by:
A) O, Y, Z and N,
B) P, Y, M and Z,
C) O, X, M and Z
D) P, X, Z and N

Answer 1

Hint:When light ray falls on the surface of the glass prism and enters into it, due to refraction it bends towards ground and finally at the time of leaving the prism another refraction happens and it bends further. Total angle of deviation in this process depends on the angle of incidence of light and on the angle of the prism.

Explanation:
Angle of prism: The angle between two surfaces of the prism from where the refraction of light ray is happening is known as the angle of prism. In the given picture the angle of the prism is represented by O.

Angle of incidence: In geometry of optics angle of incidence is the angle between the incident ray on a surface and the line perpendicular to the surface at that point of incidence. In this picture, the angle of incidence is represented by X.

Angle of emergence: Angle of emergence is the angle between the emerging ray after emergence from some surface and the line perpendicular to the surface at that point of emergence. In this picture, the angle of incidence is represented by M.

Angle of deviation: Angle of deviation is the angle between the incident and emerging ray in this whole prism setup. It gives us the total angular deviation formed from the actual ray due to the presence of the prism. Here, the angle of deviation is represented by Z.

Correct answer:
The angle of prism, angle of incidence, angle of emergence and angle of deviation respectively have been represented by (c) i.e. O, X, M and Z.

Note:Here, a student might get confused while choosing angle of incidence and angle of emergence. For angle of incidence don’t get confused between X and Y, always remember that angle of incidence is always measured w.r.t the normal to the surface, not with the actual surface. And the same argument holds for the angle of emergence also.