Solid State Physics ||Unit 01||Crystal Diffraction & Reciprocal Lattice ||💥BRAGG'S LAW 💥||mynotes ||#physicsextreem

W.L Bragg found that position of the diffracted beams produced by a crystal can be determined by a simple model .This model assumes that xrays are reflected specularly from the various planes of atoms in the crystals. The diffracted beams are found only for special case in which the reflections from parallel planes of atoms  interfere constructively.

Xray is most useful for this purpose because its wavelength is nearly equal to (2d) {It is Bragg Condition}

We consider in the crystal a series of atomic planes which are considered to be partly reflecting for radiation of wavelength  (lambda) and which are spaced equal distance "d" apart. The radiation is incident in the plane of paper. The path difference for rays reflected from adjacent planes is 2d sin@ . 

Reinforcement of the radiation reflected from successive planes will occur when the path difference is an integral no "n" of wavelengths.

( refrence:---https://www.xtal.iqfr.csic.es/Cristalografia/parte_05_5-en.html )

This is Bragg's law.Here n being the order of diffrection .It is clear that there are only certain directions in which the reflections of a given wavelength from all parallel planes add up in phase to give a strong diffracted beam. We also reached the conclusion that a beam of monochromatic Xrays , incident on a crystal with an arbitrary angle @. 

(Ref :-- RL Singhal, C Kittel, Gupta-kumar)