A monochromatic light beam of wavelength
xrb8t-rs4 l +q λ is diffracted at a single slit of wid
4t+- 8sr qblrxth $b$. 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 $w$?