Planck had suggested that atoms can emit or absorb radiation in bursts called quanta. Einstein proposed that
quantum nature is an inherent property of radiation itself.
When light falls on some metals, electrons are emitted from their surfaces. This is known as the photoelectric
effect.
Classical theory is inadequate in explaining several features of photoelectric effect. For instance, the emission of
photoelectrons is practically instantaneous without any measurable time lag between shing of light and emission of photoelectrons.
The photoelectrons are not emitted, no matter how intense is the radiation, unless the frequency of incident radiation
exceeeds a critical value.
Einstein's was able to explain photoelectric effect on the basis of photon theory of light. Einstein's euation states
that the maximum kinetic energy of emitted photoelectrons is the difference between the energy of the incident quantum and the work-function for the material.
Congratulations! you have finished Lecture-24. To view the next Lecture select it from the left hand side of the page.
