A beam of light `(lamda=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

Options

A. `1.2 cm`
B. `1.2` mm
C. `2.4` cm
D. `2.4` mm

Answer

D

Explanation

Here, `lambda=600 nm=600xx10^(-9)m`
`a=1mm=10^(-3)m,D=2m`
Distance between the first dark fringes on either side of the central bright fringe is also the width of central maximum.
Width of central maximum=`(2lambdaD)/(a)`
`=(2xx600xx10^(-9)mxx2m)/(10^(-3)m)=24xx10^(-4)m=2.4xx10^(-3)m`
`=2.4mm`