A monochromatic light beam of w
,vy,m5 6 -vb fqp6jo;pmog5mo5mc6ypavelength λ is diffracted at a single slit of width
65y 5g6f,5oo vvompc-qm ;mpm ,6y pbj $b$. 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 $w$?