Questions in semiconductor

Select	Question
	To make a PN junction conducting
	Which is the wrong statement in following sentences? A device in which P and N-type semiconductors are used is more useful than a vacuum type because
	The depletion layer in silicon diode is $1 \mu m$ wide and the knee potential is $0.6 V$, then the electric field in the depletion layer will be
	In the diagram, the input is across the terminals A and C and the output is across the terminals B and D, then the output is
	The current through an ideal PN-junction shown in the following circuit diagram will be
	If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be
	In a full wave rectifiers, input ac current has a frequency $\nu$. The output frequency of current is
	A diode having potential difference 0.5 V across its junction which does not depend on current, is connected in series with resistance of 20 $\Omega$ across source. If 0.1 A passes through resistance then what is the voltage of the source