May 6 2014
A photoelectric effect is a result of an emission of electrons when a matter is exposed to electromagnetic radiations, such as photons of light. Electrons thus emitted are called photoelectrons. In 1905, Albert Einstein explained the principle of photoelectric effect as being the consequence of transportation of light energy in discrete quantized packets.
Experiments on the photoelectric effect have explored a number of concepts related to the quantum nature of electrons and light, in addition to the concept of wave-particle duality. The photoelectric effect occurs at energies up to over 1MeV in elements with a high atomic number.
Emission Mechanism
The energy of the photons of a light beam is proportional to the light frequency. During the photoemission process, an electron within a material is ejected if it acquires more energy than the work function of the material after absorbing the energy of one photon.
Under the conditions of low photon energy, the electrons will be trapped inside the material. The number of photons in the light beam increases with the increase in light intensity, which in turn excites a large number of electrons.
It is essential to absorb all the energy from each photon to liberate the electrons from atomic binding. Upon absorption, some of the energy of the photon contributes to the kinetic energy of electrons by releasing free particles.
Applications of Photoelectric Effect
The following are applications that make use of the photoelectric effect:
- Image sensors
- Photomultipliers
- Solar cells
- Photoelectron spectroscopy
- Gold-leaf electroscopes
- Spacecrafts
References