Question

A parallel beam of monochromatic light of wavelength 450 m passes through a long slit of width 0.2 mm. find the angular divergence in which most of the light is diffracted.

Answer 1

Most of the light is diffracted between the two first order minima. These minima occur at angles given by `bsintheta=+-lamda`.
or `sintheta=+-lamda/b`
`=+-(450x10^-9m)/(0.2xx10^-3m)=+-2.25xx10^-3`
`theta=+-2.25xx10^-3rad.`
The angular divergence `=4.5xx10^-3 rad`.