$A$ $p-n$ photodiode is fabricated from a semiconductor with a band gap of $1.4 \ eV$. It can detect a signal of wavelength:

Consider a situation in which reverse biased current of a particular $P-N$ junction increases when it is exposed to light of wavelength $\lambda \le 621 \, nm$. During this process,enhancement in carrier concentration takes place due to the generation of hole-electron pairs. The value of the band gap is nearly (in $eV$):

An $LED$ is manufactured using zinc selenide; then it emits:

Identify the mismatch out of the following.

$LED$ is constructed from $GaAsP$ semiconducting material. The energy gap of this $LED$ is $1.9\, eV$. Calculate the wavelength of light emitted and its colour.
$[h = 6.63 \times 10^{-34} \, Js$ and $c = 3 \times 10^{8} \, ms^{-1}]$

In a $p-n$ junction solar cell,the value of photo-electromotive force produced by monochromatic light is proportional to the