A monochromatic light beam of
fbnkq5hzo2 / 4 wavelength λ is diffracted at a single slit of widt
4ko/fn 5bhzq2h $b$. 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 $w$?