Assertion : Diode lasers are used as optical sources in optical communication.
Reason : Diode lasers consume less energy.

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

In the working of a photodiode,the reverse current depends on

Conductivity of a photodiode starts changing only if the wavelength of incident light is < 660 \, nm. The band gap of the photodiode is found to be $\left(\frac{x}{8}\right) eV$. The value of $x$ is: (Given, $h=6.6 \times 10^{-34} \, Js, c=3 \times 10^8 \, m/s, e=1.6 \times 10^{-19} \, C$)

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:

The given characteristic curve is related to which electronic device?