Answer to Question #101167 in Physical Chemistry for GHOST

Question

State bragg law.list the assumption made by bragg in deriving bragg equation.

Answer 1

Bragg's law:

The fundamental law of x-ray crystallography, $nλ = 2dsinθ$ , where n is an integer, λ is the wavelength of a beam of x-rays incident on a crystal with lattice planes separated by distance d, and θ is the Bragg angle.

Bragg diffraction occurs when electromagnetic radiation or waves with wavelength comparable to atomic spacings are incident upon a crystalline sample and are scattered in a specular fashion by the atoms in the system, and undergo constructive interference. For a crystalline solid, the waves are scattered from lattice planes separated by the interplanar distance d. Where the scattered waves interfere constructively, they remain in phase since the path length of each wave is equal to an integer multiple of the wavelength.

Assumptions:

1) Falling light is a single monochromatic wave

2) If only two planes of atoms were diffracting, then the transition from constructive to destructive

interference would be gradual as the angle is varied.

3) Grating is periodic