Question

How can energy required for electron emission from the surface be supplied?

Answer 1

Energy required for electron emission from the surface be supplied by:

Photoelectric effect

1. The photoelectric effect is the phenomenon of the emission of electrons when an incident light of energy greater than the work function of the metal falls on it.
2. The energy responsible for the photoelectric effect is photon energy.
3. The electrons of the metal are emitted in this process, these photo-generated electrons are called photoelectrons.
4. In the case of the photoelectric effect, the energy of the incident ray is greater than the work function of the metal.
5. The equation of photoelectric effect is given by,

$h\nu =h{\nu }_0+\frac{1}{2}m{v}^2$

where $h$ is the planks constant, $\nu$ is the frequency of incident light, ${\nu }_0$ is the threshold frequency and $\frac{1}{2}m{v}^2$ is the kinetic energy of the ejected electron.

This kinetic energy gained by the electron is used by it to escape from the metal.

Thermionic emission

1. By heating the metal, sufficient thermal energy can be transferred to free electrons which enable them to come out of the metal.

Field emission

1. By applying strong electric field, electrons can come out of the metal like in a spark plug.