$A$ $p-n$ photodiode is manufactured from a semiconductor with a band gap of $3.1 \,eV$. Which of the following wavelengths can be detected by it?

For detecting light intensity,we use:

$A$ $p-n$ photodiode is fabricated from a semiconductor with a band gap of $2.5 \, eV$. It can detect a signal of wavelength:

$A$ 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 energy band gap of a semiconducting material required to produce a violet (wavelength $= 4000 \, \mathring{A}$) $LED$ is $....... \, \text{eV}$. (Round off to the nearest integer).

$A$ 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 $nm$?