A monochromatic light beam o
*e4cw1qu z y,mq0onhemv;b(f1 5u y6b f wavelength λ is diffracted at a single slit of widt
0nh b5,oy b *zqf1qv1y6;w4c(e euu mmh $b$. 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 $w$?