A monochromatic light beam of waveleng
3 3 g4nd*vdxadjxfs:fe8 :o,nth λ is diffracted at a single slit of wid
vfj efn8 d4sda3on: *,:gxx3dth $b$. 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 $w$?