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

Statement $-1$: $A$ photodiode operates in reverse bias.
Statement $-2$: The fractional change due to the photo-effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the forward bias current.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Photodiodes are preferably operated in reverse bias condition for light intensity measurement.
Reason $R$: The current in the forward bias is more than the current in the reverse bias for a $p-n$ junction diode.
In the light of the above statements,choose the correct answer from the options given below:

In a $PN$ junction photocell,the value of the photo-electromotive force produced by monochromatic light is proportional to

Three photodiodes $D_{1}, D_{2}$ and $D_{3}$ are made of semiconductors having band gaps of $2.5 eV, 2 eV$ and $3 eV$,respectively. Which one will be able to detect light of wavelength $600 nm$?

The schematic symbol of a light emitting diode $(LED)$ is: