A monochromatic light beam of wavelength λ is diffracted at
fh itlk6q7w 0/ a single slit of widt
l 7h6/tk0 fiwqh $b$. 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 $w$?