A monochromatic light beam of wavelength λ is
m 4j9 )wy uf4*t)tpi+1 akovyzb6zi7 xbp;ee( diffracted at a single slit of width
wji be) yzp a16ozxmiy4) pt4v9(b7f k+;u te* $b$. 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 $w$?