The first diffraction minima due to a single diffraction is at $30^{\circ}$ for a light of wave length $5000A^{\circ}$ the width of slit is

Question

$(a)\;1.0 \times 10^{-4} \;cm \\ (b)\;5 \times 10^{-5} \;cm \\ (c)\;2.5 \times 10^{-4} \;cm \\ (d)\;2.5 \times 10^{-5} \;cm $