The first diffraction minimum due to the single slit diffraction is seen at $\theta = 30^{\circ}$ for a light of wavelength $5000\,\AA$ falling perpendicularly on the slit. The width of the slit is\\
(1) $2.5\times10^{-5}\mathrm{~cm}$\\
(2) $1.25\times10^{-5}\mathrm{~cm}$\\
(3) $10\times10^{-5}\mathrm{~cm}$\\
(4) $5\times10^{-5}\mathrm{~cm}$