Question

The diffraction of barium with X-radiation of wavelength 2.29Å gives a first – order reflection at 30°. What is the distance between the diffracted planes.

• A. 3.29 Å
• B. 4.39 Å
• C. 2.29 Å
• D. 6.29 Å

Answer 1

Answer: (C)

2.29 Å

Answer 2

Using Bragg's equation $2d\sin\theta = n\lambda$

$d = \frac{n\lambda}{2\sin\theta}$, where d is the distance between two diffracted planes, $\theta$ the angle to have maximum intensity of diffracted X-ray beam, $n$ the order of reflection and $\lambda$ is the wavelength

$\therefore$ $d = \frac { 1 \times 2.29 \AA } { 2 \times \sin 30 ^ { \circ } } = 2.29 \AA$ $\left( \sin 30^{o} = \frac{1}{2} \right)$