In a single slit diffraction experiment, the width of the slit is increased. How will the (i) size and (ii) intensity of central bright band be affected ? Justify your answer.

Explanation

We know that angular width of central bright band in a single slit diffraction pattern is given as
`alpha=2 theta= (2lambda)/(a)` where a = slit width
and size of central bright band x = `D alpha=(2lambdaD)/(a)` where D is the distance of screen from the slit.
(i) If slit width .a. is increased then obviously a as well as x will decrease i.e., central bright band will become narrower.
(ii) On increasing the size of slit more light passes through it and the size of central bright band is decreased. Therefore, it is very much clear that intensity of central bright band will definitely increase.