A monochromatic light beam of wavelength λ is diffracted at a single slit of
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nwoq cc3( )a2fbq1p, ifybr2520 efiwh $b$. 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 $w$?