A monochromatic light beam of wav
t/fqob/kni ut (z*9ej, h7j6 uky9j u9elength λ is diffracted at a single slit of width
7 9quh,6yfbju/ *tu 9zoek( t9/ njkji $b$. 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 $w$?