A monochromatic light beam of wavelength λ
q x4onmtmoglryb *sne 0f2+x0/u5, c - is diffracted at a single slit of width
s u02-c,m*n+bf0t/ge 5xon r ymxqol4 $b$. 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 $w$?