Show that for the diamond structure the Fourier component U-G of the crystal potential seen by an electron is equal to zero for G=2A, where A is a basis vector in the reciprocal lattice reffered to the conventional cubic cell

When you turn on a battery-operated device, an electrical circuit is

What are similarities and differences between refraction, reflection, diffraction and absorption?

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e