In the figure shown S is a point monochromatic light source of frequency `6xx10^(14)Hz`.M is a concave mirror of radius of curvature 20 cm and L is a thin converging lens of focal length 3.75 cm AB is the principal axis of M and L.
Light reflected from the mirror and refracted from the lens in succession reaches the screen. An interference pattern is obtained on the screen by this arrangement.
Q. Fringe width is

Options

A. 1 mm
B. 0.5 mm
C. 1.5 mm
D. 0.25 mm

Answer

B

Explanation

`beta=(5xx10^(-7)xx50xx10^(-2))/(0.5xx10^(-3))=5xx10^(-4)m=0.5mm`