Question

Photovoltaic cells produce electricity by using
(A) Wind energy
(B) Solar energy
(C) Geothermal energy
(D) Mechanical energy of water

Answer 1

Hint
The word photovoltaic means voltage from light. This is enough to understand that when sunlight is incident on these cells, it leads to the production of electricity.

Complete step by step answer
Photovoltaic cell or solar cell is a p-n junction diode that transforms sunlight to electricity with a large conversion efficiency. When light of a particular wavelength is incident on these cells, the photons transfer their energy to electrons which then jump from valence band to conduction band, thus becoming free to conduct current. When light falls on the diode, photons are absorbed to produce electron-hole pairs. These electrons and holes reach the depletion region and slide towards their majority carrier side.
When the diode is open-circuited, the electrons and holes collected on the two sides of the junction produce an open circuited voltage ${V_{oc}}$. In the presence of a load resistance ${R_L}$, a current $I$ flows in the circuit.
Photovoltaic cells are made of silicon, gallium arsenide etc.
Over the recent years they have been steadily gaining popularity because of their sustainability and improvements leading to price reductions.
So, we can establish the fact that photovoltaic cells produce electricity by using solar power.
Therefore, the correct answer is (B).

Note
The energy gap between the valence band and the conduction band is the minimum amount of energy which is required for the electrons to be able to jump and become available for conduction. However some of the energy coming from the sun is not enough to overcome this band gap. So that lowers the number of electrons available for conduction by a considerable amount. So, the theoretical efficiency of a silicon photovoltaic cell is about $33\% $.