Einstein’s photoelectric equation

Photoelectric effect: The photoelectric effect is a physical phenomenon that occurs when a metal surface is struck by light of a specific frequency. Heinrich Hertz discovered this phenomenon back in 1887, and later Lenard confirmed it in 1902. Still, there were only a few anomalies since Maxwell’s electromagnetic wave theory of light could not explain the photoelectric effect. Einstein took advantage of Planck’s concept of light as a particle to address the previously occurring problem with the photoelectric effect. Einstein demonstrated that each particle of light, known as a photon or quanta, carries energy in the form of packets that vary in size depending on the frequency of the light being transmitted.

Energy(E) carried by each particle of light (photon) can be written as- E = hν where, (ν) is the light’s frequency and h is known as the Planck’s constant (6.6261 × 10-34 Js).

And Einstein’s Photoelectric equation is given by,

K.E. =  hν – Ø0

Where K.E. is the kinetic energy of the photoelectrons

Ø0 is the work function of the metal

hν is the energy of the photons

Photoelectric Effect

In 1887, Hertz noticed that electrons are emitted from a metal surface when electromagnetic radiation falls on it. In 1888, Hallwachs showed experimentally that electrons are emitted from the Zinc plate when ultraviolet rays fall on the plate.

This phenomenon of emission of electrons from a metallic surface, when illuminated by the light of appropriate wavelength or frequency, is called the photoelectric effect. The electrons radiated in this process are called photoelectrons and the current which is produced in the circuit is called photoelectric current.

The photoelectric effect in general is a phenomenon exhibited by all the substances when illuminated by radiation of a suitable wavelength.

Particle nature of light 

When we talk about particles, we’re talking about little pieces of stuff. Although light is made up of particles, we refer to them as photons since they are light particles. When Sir Isaac Newton used a prism to split sunlight into multiple colours, the perimeter of the shadows he cast was exceedingly crisp and distinct, leading him to conclude, in 1700, that light was made up of particles.

As an elementary particle and a quantum of light, a photon is defined thus: Using the equation E = hv, we can figure out how much energy a photon has. Energy is denoted by E, while h is Planck’s constant and v is the frequency of photons. In this case, raising the intensity of light indicates that we have increased the number of photons that pass an area in a certain amount of time. Another advantage of photons is that they have no mass yet are considered stable subatomic particles. A photon may transmit energy to a different particle during an interaction.

Photons

Essentially, a photon is a subatomic particle of light. The particle of light is called a photon or quanta.

• The equation E = hv describes the energy of a photon. Because of this, it has the same momentum and speed as light.

• The momentum p and energy E of every photon with frequency v are the same regardless of the intensity of the radiation.

• As light intensity increases, the number of photons passing a specific region per unit time increases proportionally. Radiation energy is not affected by this factor.

• Electric and magnetic fields do not affect a photon’s behaviour. 

• Electricity is not a factor in this case.

• A photon has no mass, i.e. it has no gravitational attraction to any other particle.

• In terms of stability, it is an excellent candidate for use in physics.

• The emission or absorption of radiation can result in the creation or destruction of photons, respectively.

• During a photon-electron collision, both total energy and momentum are preserved.

• Without an external energy source, a photon can’t decay.

• During contact with other particles, the energy of a photon can be transmitted.

• Unlike electrons, which have spin (±½), a photon has a spin ±1. Its spin axis runs parallel to the direction in which it is travelling. This feature of photons allows light to be polarised in the first place.

Photoelectric Work Function

The photoelectric effect is the removal of the electron from an atom of a photosensitive material that is the most loosely linked. The surface material’s photoelectric work function (Ø0) is defined as the smallest amount of energy required to eject an electron from a specific surface when the surface material is a semiconductor. The work function of a metal surface is one of its distinguishing characteristics.

The work function can be expressed mathematically as

Ø0 = hv0

Conclusion

• Einstein’s photoelectric effect is caused when the photons resent in the light interact with the electrons in the metal

• Each of the photons interacts with 1 electron.

• The energy of the incident photon is used in releasing the electrons from the surface and to transmit energy to the ejected electrons.

• The minimum energy required to emit electrons from the surface is called the work function.

The energy of the incident photon should be more than the work function.