What happens to the width of the central diffraction pattern (in the single slit experiment) as the slit width is changed and why?

width of fringes are increased

Explanation:

The width of central maxima is given by the following expression

Width = 2 x Dλ / d

D is distance of screen from source, d is slit width and λ is wavelength of light source. Here we see, on d getting decreased, width will increase because d is in denominator.

Due to increased width, position of a fringe moves away from the centre.