Certain planes of a crystal of halite have a spacing of 0.399 nm. the crystal is irradiated by a beam of x-rays. first order constructive interference occurs when the beam makes an angle of 20° with the planes. what is the wavelength of the x-rays?

The wavelength of x-ray is 0.272 nm.

Explanation:

Inter planer spacing, d = 0.399 nm = 3.99 × 10⁻¹⁰ m

First order constructive interference occurs when the beam makes an angle of 20° with the planes. We need to find the wavelength of the x-rays. The condition for constructive interference is given by :

Here, n = 1

So, the  wavelength of the x-rays is 0.272 nm. Hence, this is the required solution.