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

Explanation

`sin theta_(1)=(lamda)/a`
But `sin theta_(1)=(2.5xx10^(-3))/1=2.5xx10^(-3)`
`a=(lamda)/(sin theta_(1))=(50xx10^(-9))/(2.5xx10^(-3))=0.2mm`