A monochromatic light beam of waveleng
oo pm6 n0w2qa:th λ is diffracted at a single slit of widt
pwm 0o2onq:a6h $b$. 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 $w$?