A monochromatic light beam of wav
x8 r6irm r9 cxfst+x,,j9)kwxelength λ is diffracted at a single slit of widt
,)ks8rm9t+xf6 w j,xxrx c i9rh $b$. 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 $w$?