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# 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

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

For Diffraction minima
$d \sin \theta = n \lambda$
1st order $n=1$
$d \sin 30 = 1\times 5000 \times 10^{-10}$
$d \times \large\frac{1}{2}$$= 5000 \times 10^{-10}$
$d= 10000 \times 10^{-10} \;m$
$d= 1 \times 10^{-4} \;cm$
Hence a is the correct answer.