A monochromatic light beam of wavelength λ is diffracted at a single slit
a ,ec.g:-r5 bjjuudn dl5q;n; of width
n beu-5c. jddal5r ;ju:g;,qn$b$. 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 $w$?