Question

A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen lmaway. 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.

Answer 1

Here, `lambda=50nm =5xx10^(-7)m, D=1m,y=2.5mm= 2.5 xx 10^(-3)m, d=?`
`sin theta=(lambda)/(d)=(y)/(D) therefore (lambdaD)/(y)=(5xx10^(-7)xx1)/(2.5xx10^(-3))=2xx10^(-4)m=0.2mm`