(a) sketch mobility as a function of temperature, pointing out the temperature dependences in different regimes. if two different sources of scattering give mobilities of 250cm2/v s and 500cm2/v s, what is the overall mobility? hint: use - . [2+21 (b) consider an experiment where excess electrons are generated in a burst at 0 at z zo in a semiconductor, resulting in a concentration profile given by n(z; t = 0) = δ(z-zo). sketch the shapes of the concentration profile n(z, t) vs z for various times after the initial burst. give reasons for your answer. [2] now consider there is an additional applied uniform electric field eo in the z-direction. sketch the shapes of the concentration profile n(z, t) vs z for various times after the initial burst. describe what happens if, now, a magnetic field is applied in the x-direction. hint: remember the lorentz equation f- q(e +vx b) used for hall measurement. give reasons for your answer in every case.