A monochromatic light beam of
t:35 1 djvermrqm6ah0 wavelength λ is diffracted at a single slit of width
dtq5mr a3er1 vmh0 j:6 $b$. 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 $w$?