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

If a semiconductor photodiode can detect a photon with a maximum wavelength of $400\, nm$, then its band gap energy is (Given: Planck's constant $h = 6.63 \times 10^{-34}\, J \cdot s$, Speed of light $c = 3 \times 10^{8}\, m/s$) (in $ eV$)

The energy gap of an $LED$ is $2.4 eV$. When the $LED$ is switched $ON$,the momentum of the emitted photons is

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

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

Identify the correct circuit diagrams for the normal operation from the following.