Photo cells are used for the
Reproduction of pictures from the cinema film
Reproduction of sound from the cinema film
Automatic switching of street light
$(b)$ and $(c)$ both
Energy conversion in a photoelectric cell takes place from
If a source of power $4\,kW$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called
If the energy of the photon is increased by a factor of $4$, then its momentum
Kinetic energy with which the electrons are emitted from the metal surface due to photoelectric effect is