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.

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

the temperature and the pressure affect solubility. temperature affects by changing the properties of the solvent. the increase in pressure increases solubility, the decrease in pressure decreases solubility.

im sorry i dont know