Question

A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observe on screen 1 m away. It is observed that the first minimum is at a distance of `2.5 mm` from the centre of the screen. Find the width of the slit.
A. 0.2 mm
B. 1 mm
C. 2 mm
D. 1.5 mm

Answer 1

Correct Answer - A
Width of slit, `d=(n lambda D)/(x)`
Here, `n=1, D=1m,x=2.5mm=2.5xx10^(-3)m`
`lambda=500 nm=500 xx 10^(-9)m`
` :. d=(1xx500xx10^(-9)xx1)/(2.5xx10^(-3))=2 xx10^(-4)m=0.2mm`