A monochromatic light beam of wavelen
j3:/60pj(6q;ognbu l) eoz5svtq ylv ,;uqhngth λ is diffracted at a single slit of widt
v6t,buopl;n5j)q/ 6 ;3qequhljz0ygosv n : (h $b$. 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 $w$?