A monochromatic light beam
kb*q)v i2r9nngnk,eb/m46d s of wavelength λ is diffracted at a single slit of widt
r m)bq4b 2div6* /ken s9k,ngnh $b$. 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 $w$?