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

$A$ photodetector is fabricated from a semiconductor with a band gap $E_g = 0.73 \, eV$. What is the maximum wavelength (in $nm$) it can detect?

What are optoelectronic devices? Give the names of such major devices.

$A$ $p-n$ photodiode is fabricated from a semiconductor with a band gap of $2.8 \; eV$. Can it detect a wavelength of $6000 \; nm$?

The semiconductor used for the fabrication of visible LEDs must at least have a band gap of (in $eV$)

$A$ red $LED$ emits light at $0.1 \ W$ uniformly in all directions. The amplitude of the electric field of the light at a distance of $1 \ m$ from the diode is.... $V \ m^{-1}$