The energy e of an electron in the conduction band of a metal is related to its wave vector k by: e = a sinº ka, where a is a constant and a is the atomic lattice spacing. if a = 2 x 10-10 m then the fermi wave vector is 2.618 x 100 m-1 and fermi energy is 1 ev. determine the effective mass of conduction electrons at the fermi level. (1) (b) a thin, pure (intrinsic) semiconductor is found to transmit light in the infra-red, but as the frequency of the light is increased, the semiconductor suddenly becomes absorptive. suggest a reason for this phenomena. (c) derive an equation for the conductivity of an intrinsic semiconductor, using con- cepts such as the fermi level, the band-gap, mobility, carrier density and fermi- dirac distribution. assume a constant density of states for electrons and holes.

Acombination reaction is when two or more combine to form one product. a decomposition reaction is when a substance breaks down into two or more simpler substances in a chemical reaction.

Find the magnetic field a distance r from the center of a long wire that has radius a and carries a uniform current per unit area j in the positive z direction.

In the future, people will only enjoy one sport: electrodisc. in this sport, you gain points when you cause metallic discs hovering on a field to exchange charge. you are an electrodisc player playing the popular four disc variant. the disks have charges of qa = −8.0 µc, qb = −2.0 µc, qc = +5.0 µc, and qd = +12.0 µc. (1) you bring two disks together and then separate them. you measure the resulting charge of these two disks and find that it is +5.0 µc per disk. which two disks did you bring together? (a) a and b (b) a and c (c)a and d (d)b and c(e) b and d (f) c and d. (2) you bring three disks together and then separate them. you measure the resulting charge of these three disks and find that it is +3.0 µc per disk. which three disks did you bring together? a, b, and c (a) a, b, and d (c) a, c, and d (d) b, c, and d. (3) given the resulting charge of each disk measured in (b) is +3.0 µc, how many electrons would you need to add to a disk of this charge to electrically neutralize it? electrons