Light of wavelength $500\,\text{nm}$ falls on a single slit of width $0.1\,\text{mm}$. The angular width of the central maximum in the resulting diffraction pattern is:

The angular width of the central maximum in single-slit diffraction is $2\lambda/a$, where $a$ is the slit width. $2\lambda/a = 2 \times 500 \times 10^{-9} / (0.1 \times 10^{-3}) = 10^{-2}\,\text{rad}$.