A monochromatic light beam of wavelength λ
/vh.k9mv h jh5*d3rbwh4o)4 wrmy/wf is diffracted at a single slit of wid
.j4wvm3 mw* 4hrk//hh9vf5 h y)owdbrth $b$. 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 $w$?