In deriving the single slit diffraction pattern,

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

$\therefore$ Width of each slit, $d^{\prime}=\frac{d}{n}$

Angle of diffraction is given by the relation,

$\theta=\frac{\frac{d}{d^{\prime}} \lambda}{d}=\frac{\lambda}{d^{\prime}}$

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