A monochromatic light beam of wavelength
g*fo)ujt5js:vtw ) 3qwb- ui7n-w5tt λ is diffracted at a single slit of width
-ufi -ot7wquwj)w nt 5*5sbg3 ):vtt j $b$. 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 $w$?