A monochromatic light beam of
c3t7y+o( jilzhiv:1 k wavelength λ is diffracted at a single slit of width
ot(hj vzi7:31i lk +yc$b$. 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 $w$?