Red light of wavelength `6500 Å` from a distant source falls on a slit `0.50 mm` wide. Calculate the distance between first two dark bands on each side of central bright band in the diffraction pattern observed on a screen placed `1.8 m` from the slit.

Explanation

`Given lamda=6500 dotA=65 times10^-8 m`
`a=0.5 mm=0.5 times10^-3 m,D=1.8 m`
Required distance between first two dark bands will be equal to width of central maxima
`w_x=(2 lamdaD)/a=(2 times6500 times10^-10 times18)/(0.5 times10^-3)`
`=468 times10^-5 m4.68 mm`