Question

A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is
A. 1.2 cm
B. 1.2 mm
C. 2.0 cm
D. 2.0 mm

Answer 1

Correct Answer - D
Fringe width, `beta=(lambdaD)/(d)=(500xx10^(-9)xx2)/(1xx10^(-3))=10xx10^(-4)m`
So, distance between the first dark fringes on eitherside of the central bright fringe
`X=2beta=2xx10xx10^(-4)m`
`=20xx10^(-4)m=2.0mm`