For plane (200):

$d= \dfrac{a}{\sqrt {h^2+k^2+l^2}}$

$d=\dfrac{2.814 \times 10^{-10}}{\sqrt {2^2+0+0}}$

$\therefore d=\dfrac{2.814 \times 10^{-10}}{ 2}$

$\therefore d=1.407 \times 10^{-10}\ m$

Using Bragg's law

$n\lambda=2d \sin\theta$

$\sin\theta = \dfrac{n\lambda}{ 2d}$

$\sin\theta = \dfrac{2 \times0.71 \times 10^{-10} }{ 2\times1.407\times 10^{-10}}$

$\sin\theta =0.5046$

$\theta=\sin^{-1}{0.5046}$

$\therefore \theta=30.31^{\circ}$

∴ Bragg's angle …