# Solid state physics

#### fabsuk

1 few questions here

Does anyone know websites that i can get solid state physics problems and answers.

2ndly How do you show a semiconductor of type 1
behaves as a perfect diamagnet.

I know by drawing a diagram but don't how to show it

3rdly

what is the definition of an 'optical branch' and 'acoustic branch' for chain of atoms. I cant find
clear definitions

4thly

explain why kc1 which has the nac1 structure scatters X rays as though it had the simple cubic structure with half the true lattice spacing

All these questions are bothering and cant find them in books.

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#### Dr Transport

Gold Member
The optical and acoustic branches come about because the lattice has a basis, i.e. two different atomic species. The acoustic branch is due to the atoms oscillating in phase with each other. The optical branch is seen when the atoms of different masses oscillate out of phase with each other.