A monochromatic light beam of wavelength
, 8mejxqtj/ sl,uq02l λ is diffracted at a single slit of width
ul0,/tx, sq8 mlqejj 2 $b$. 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 $w$?