In the nearly-free-electron model, energy gaps occur at values of wavevector corre- sponding to bragg reflection. (i) using this model, calculate the directions in a simple cubic structure in which the first, second and third energy gaps occur (ii) calculate the electron energies at which these gaps occur for a lattice constant a 4x 10-10 m. (b) the energy e of an electron in the conduction band of a metal is related to the wavevector k by e 2x 10-10 m. given the fermi wavevector is 2.618 x 109 m-1 and the fermi a sin2 ka. here, a is a constant and a is the lattice spacing - energy is 1 ev, determine the effective mass of the conduction electrons measured in a transport experiment that probes the electrons at the fermi level

The plum pudding model of the atom state that ?

The frequency of vibrations of a vibrating violin string is given by f = 1 2l t ρ where l is the length of the string, t is its tension, and ρ is its linear density.† (a) find the rate of change of the frequency with respect to the following. (i) the length (when t and ρ are constant) (ii) the tension (when l and ρ are constant) (iii) the linear density (when l and t are constant) (b) the pitch of a note (how high or low the note sounds) is determined by the frequency f. (the higher the frequency, the higher the pitch.) use the signs of the derivatives in part (a) to determine what happens to the pitch of a note for the following. (i) when the effective length of a string is decreased by placing a finger on the string so a shorter portion of the string vibrates df dl 0 and l is ⇒ f is ⇒ (ii) when the tension is increased by turning a tuning peg df dt 0 and t is ⇒ f is ⇒ (iii) when the linear density is increased by switching to another string df dρ 0 and ρ is ⇒ f is ⇒

The junction rule describes the conservation of which quantity? note that this rule applies only to circuits that are in a steady state.