A parallel beam of light of 450 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1.5 m away. It is observed that the first minimum is at a distance of 3 mm from the centre of the screen. Calculate the width of the slit.

Explanation

The distance of the nth minimum from the centre of the screen, `x_(n)=(n D lambda)/(a)`
Where D - distance
`lambda` - wave length
a - width of the slit
For first minimum, `n=1, 3 xx 10^(-3)=(1 xx (1.5)xx(450 xx 10^(-9)))/(a)a=(1 xx (1.5)xx(450 xx 10^(-9)))/(3 xx 10^(-3))a=0.225 mm`.