A monochromatic light beam of wavelength λ is diff
b4-zkvlex76+i u6i ps racted at a single slit of wid
7bx kp lzuie64 -+s6vith $b$. 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 $w$?