A monochromatic light beam o
vl7rkfbyuh8 3 2:;xbk f wavelength λ is diffracted at a single slit of width
xbr 3kkbu8v;f yl27: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 $w$?