A monochromatic light beam of
a s)h+u lz fv69psw:m:x5jt1s wavelength λ is diffracted at a single slit of width
9t m6:pl s)haws:xj+fu z5sv1 $b$. 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 $w$?