A monochromatic light beam of wavelength λ
c 5-o9, 8yvoo usa9wiw is diffracted at a single slit of width
c oo,-s 9ui9ovw5a8 wy $b$. 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 $w$?