Light of wavelength $600\mathrm{ n}\mathrm{m}$ is incident normally on a slit of width $0.2\mathrm{ m}\mathrm{m}$. The angular width of the central maxima in the diffraction pattern is $n\times {10}^{-3} \mathrm{rad}$, then what is the value of $n$? (measured from minimum to minimum)