Question

Why is the intensity maximum at the central maximum on the diffraction pattern?

Answer 1

Most of the light is concentrated in the broad CENTRAL DIFFRACTION MAXIMUM. . note that the width of the central diffraction maximum is inversely proportional to the width of the slit. If we increase the width size, a, the angle T at which the intensity first becomes zero decreases, resulting in a narrower central band.

Answer 2

most of the light is concentred in the broad central diffraction