The material used for solar cell should have a band gap:

$A$ photodiode is fabricated from a semiconductor with a bandgap of $2.5 \ eV$. Can it detect a wavelength of $6000 \ \mathring{A}$?

$A$ family uses $8 \; kW$ of power.
$(a)$ Direct solar energy is incident on the horizontal surface at an average rate of $200 \; W$ per square meter. If $20 \%$ of this energy can be converted to useful electrical energy, how large an area is needed to supply $8 \; kW$?
$(b)$ Compare this area to that of the roof of a typical house.

For three circuit elements $A, B$ and $C$,following observations were made in lab:
$(a)$ element $A$ cannot conduct $d.c.$ but allows $a.c.$ through it.
$(b)$ element $B$ conducts both $AC$ and $DC$ but in one direction only.
$(c)$ Element $C$,when connected across $DC$,conducts only for one polarity and emits light whose intensity first increases and then decreases with increase in applied voltage.
The elements $A, B$ and $C$ are respectively identified as

For $LED$s to emit light in the visible region of the electromagnetic spectrum,they should have an energy band gap in the range of:

Which of the following will $NOT$ be observed when a multimeter (operating in resistance measuring mode) probes connected across a component are reversed?