A monochromatic light beam of wavelength λ
4i3j 8.h+ ;xlzhqkjs wis diffracted at a single slit of width
4hk;zj+. l8js hxqi 3w $b$. After passing the slit, a diffraction pattern is observed on a screen a large distance away. The width of the central maximum is $w$.
The screen is moved closer to the slit. Which of the following changes, done separately, could result in no change in $w$?