Question

In deriving the single slit diffraction pattern, it was stated that the intensity is zero at angles of nλ/a. Justify this by suitably dividing the slit to bring out the cancellation.

Answer 1

Consider that a single slit of width d is divided into n smaller slits.

Width of each slit,

Angle of diffraction is given by the relation,

Now, each of these infinitesimally small slit sends zero intensity in directionθ. Hence, the combination of these slits will give zero intensity.