Question

Answer the following giving reason:

1. All the photo electrons do not eject with the same kinetic energy when monochromatic light is incident on a metal surface.
2. The saturation current in case (a) is different for different intensity.

Answer 1

a. The kinetic energy of released photoelectrons changes based on the starting energies of the electrons in the metal. Based on Einstein’s photoelectric equation:

K_max = hv − Φ

where:

hv = Energy of the incident photon,

Φ = Work function (minimum energy required to eject an electron),

K_max = Maximum kinetic energy of the emitted photoelectron.

Deeper electrons in metal require more energy to escape, resulting in a dispersion of kinetic energies among released photoelectrons.

b. Saturation current denotes the peak photoelectric current achieved when all emitted photoelectrons are captured by the anode. The intensity of light is directly proportional to the quantity of incident photons; thus, a greater intensity indicates a higher number of photons impacting the metal surface every second. Since each photon can eject only one electron, an increase in intensity results in a greater number of ejected electrons, hence elevating the saturation current. Nevertheless, the kinetic energy of individual electrons remains unaltered by intensity.