What is photoelectric effect and application of photoelectric effect

Photoelectric effect

Photoelectric effect theory was explained by Albert Einstein for which he was awarded the Nobel Prize.

when light of suitable frequency is allowed to fall on a metal surface, electrons are emitted from the surface. These electrons are called photoelectrons and the effect is called photoelectric effect.

The emission of a photoelectron is the result of the interaction between a single photon of the incident radiation and an electron in the metal. The photoelectric effect is widely applied in engineering. 

Photons

   A photon is neither a particle nor a wave. In phenomena like interference, diffraction, and polarization, the photon behaves like a wave.

Photoelectric cells

              

                The photoelectric cell is a device which used to convert light energy into electrical energy.

Photoelectric emission

        A photo-sensitive material there is a minimum frequency is called the threshold frequency. The photoelectric current is directly proportional to the intensity of the incident radiation, provided the frequency is greater than the threshold frequency.

Applications of photoelectric cells

• Photoelectric cells are used to reproduce sound in cinematography. Photoelectric cells are used in the study of temperature and spectra of stars. It is used in obtaining electrical energy from sunlight during space travel. Photoelectric cells are also used in burglar alarms and fire alarms. 

• The  Photoemissive cells make use of the photoelectric effect Before the introduction of photo-semiconductor devices, photoemissive cells were in wide use.  A photoemissive cell is known as the vacuum photo-diode. The most widely used photoemission material is caesium on a silver base. Vacuum Photodiodes are capable of delivering larger amounts of power than their semiconductor counterparts. But vacuum photodiodes are bulky and large weight. 

• The Photo voltaic cell generates electric potential when it is subjected to optical irradiation. Since this device is used to generate electricity from sunlight, it is popularly called as the solar cell.

•  Photethyristors are optical counterparts of thyristor devices. This device is known as the LASCR(light-activated silicon-controlled rectifier.)