The $I-V$ characteristics of a photodiode for different illumination intensities $I_1, I_2, I_3$ and $I_4$ are shown in the figure. Which of the following represents the maximum intensity?

Identify the mismatch out of the following.

$A$ 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.... $V \ m^{-1}$

$A$ $p-n$ junction is fabricated from a semiconductor with a band gap of $2.8 \ eV$. What approximate wavelength can it $NOT$ detect (in $nm$)?
[Use $h = 6 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$]

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

$A$ light emitting diode $(LED)$ is fabricated using $GaAs$ semiconducting material whose band gap is $1.42 \,eV$. The wavelength of light emitted from the $LED$ is: (in $\,nm$)