If the energy gap of a semiconductor used for the fabrication of an $LED$ is nearly $1.9 \ eV$, then the color of the light emitted by the $LED$ is

The $V-I$ characteristics of an $LED$ are correctly shown by which graph?

$A$ photodetector is made from a semiconductor $In_{0.53}Ga_{0.47}As$ with $E_g = 0.73 \, eV$. What is the maximum wavelength,which it can detect in $nm$?

$A$ solar cell is to be fabricated for efficient conversion of solar radiation to emf using material $A$. The solar cell is to be mechanically protected with the help of a coating using material $B$. If the band gap energy of materials $A$ and $B$ are $E_{A}$ and $E_{B}$ respectively,then which of the following choices is optimum for better performance of the solar cell?

The material used in the fabrication of infrared $LED$'s is

Identify the devices which work on solar energy.
$(a)$ Photodiode
$(b)$ Photovoltaic cell
$(c)$ $LED$
$(d)$ Photo-thermal devices