A monochromatic light beam of wavelengt
g;c ,b a kss0yf;- 2k4wf;.fdm f/lngdh λ is diffracted at a single slit of width
fdgmdwfla ,sk2;yf ;s.;c/f 4bn -0gk$b$. 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 $w$?