A monochromatic light beam of wavelength λ is
k4uthyr,yi (4i/ 5 eqodiffracted at a single slit of widt
,(tqhyi u /ryki e544oh $b$. 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 $w$?