Problems-2: [2x4=8pts] We know that the PN junctions, diodes, photodiodes (LEDS and photodetectors) have similar physicalstructure. But +ve and -ve terminals and direction of currents depends on how the device

is being operated.Consider following PN junctions with light shining on it, such that hv > Eg. Here Egis the bandgap of thesemiconductor material of the PN junction. A. Answer parts (i) and (ii) for each of the cases (a), (b) and (c). (i) position of positive and negative terminals (by choosing terminals 1 or 2 and assigning + or -ve sign) and (ii) direction of current through the device. (a) when there is no incident light, and PN junction is operated as a diode rectifier. (b) when PN junction is used as a photo-detector. (c) when PN junction is used as solar cell. B. Also answer in which of the above three cases, a battery should be applied to the PN junctions and in which cases we simply use PN junction as a battery.