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# Parallel beam of monochromatic light of wavelength $\lambda =4800 A^{\circ}$ is incident on a single slit of size $0.2 mm$ . The angular divergence in which most of light is diffracted is [ie between two 1st order maxima on both sides]

$(a)\;1.22 \times 10^{-3} \;rad \\ (b)\;2.4 \times 10^{-3} \;rad \\ (c)\;4.8 \times 10^{-3} \;rad \\ (d)\;2.4 \times 10^{-2} \;rad$

Can you answer this question?

$a \sin \theta=\pm nx$
$n=1$
$\sin \theta= \large\frac{\lambda}{a} =\frac{4800 \times 10^{-10}}{0.2 \times 10^{-3}}$
$\qquad= 2.4 \times 10^{-3} \;rad$
angular divergence $=2 \theta$
$\qquad= 4.8 \times 10^{-3} \;rad$
Hence c is the correct answer.
answered Jan 21, 2014 by