In a photoelectric cell,the conversion of energy takes place from:

Light of wavelength $4000 \ \mathring A$ is incident on a sodium surface,where the threshold wavelength for photoemission is $5420 \ \mathring A$. The work function of sodium is ............ $eV$.

Choose the correct option for the given statements:
Statement-$I$: The kinetic energy of photoelectrons emitted by a photosensitive surface depends on the intensity of the incident radiation.
Statement-$II$: In the photoelectric emission process,the maximum kinetic energy of the photoelectrons increases with increasing intensity of the incident light.

$A$ monochromatic beam of light of wavelength $400\,nm$ is incident normally upon a photosensitive surface ($25\%$ reflects and the rest is absorbed). This produces a radiation pressure of $5 \times 10^{-7}\,N/m^2$ on the surface. If $0.1\%$ of the incident photons produce photoelectrons,the corresponding saturation current will be $\dots \mu A$. (Consider the area of the photosensitive surface $= 5\,cm^2$)

The number of photoelectrons emitted for light of frequency $v$ (higher than the threshold frequency $v_0$) is proportional to

What is the photoelectric effect?