Albert Einstein, a German physicist, is regarded as one of the most brilliant scientists of all time. He has made contributions to general relativity, the photoelectric effect, black holes, and many other fields. He was given the Nobel Prize in the subject of Physics in the year 1921 for the discovery of the photoelectric effect.
The discovery of the photoelectric effect is one of the greatest achievements in history and in Einstein's life. He received the Nobel Prize for it. Einstein was the first to claim that light is both a wave and a particle. This is known as the wave-particle duality of light. Wave-particle duality is the basic concept of quantum mechanics and the reason for the development of solar cells and electron microscopes.
After the photoelectric effect, the irradiation of a metal surface with light of sufficient energy causes the expulsion of electrons from the metal.
So, let's try to understand what is the explanation behind the photoelectric effect.
The electrons present in the atoms on the metal surface gain energy due to the oscillating electric field of the incident light and begin to vibrate at a high frequency. If the energy of the incident radiation is greater than the work function of the metal, the electrons receive enough energy to emerge from the surface. The speed and number of electrons emitted depend on the colour and intensity of the incident radiation and the duration of the incident radiation.
When incoming radiation on light with an energy larger than the threshold value of metal strikes the surface, the metal's tightly bound electrons are released. A photo is a particle of light. When a photon collides head-on with an electron, it transfers the sum of its energy to the electron, which the electron then ejects off the surface. The photon's leftover energy creates a free negative charge known as a photoelectron.
Einstein's concept of light was both innovative and wonderful. He demonstrated an effective method of irradiation. Photons are a small collection of particles that make up light. These particles are made up of greater energy, which is also known as the quantum of radiation. As a result, light is composed of packets of energy or quantum of energy. Photons are particles that transport velocity and energy from the source of light from whence they are emitted.
The Einstein-Planck relationship states that
E = hv.. (1)
'h' = Planck's constant
‘v’= frequency of the emitted radiation.
The Photoelectric effect tests show that if the incoming light has a frequency less than the threshold frequency, no electron emission occurs. The equation shows that energy is exactly proportional to frequency, which explains the instantaneous nature of electron emissions.
Because there is no electric field beyond the surface, when the photoelectron exits the metallic surface, it is transformed to solely kinetic energy. The electron uses some of the quantum energy given by the photons to overcome the surface's chemical pull.
As a result, the kinetic energy of a photoelectron is = (photon energy imparted) - (energy used to come out of the surface).
This energy is constant for a surface and is represented by the symbol . This is known as a surface's work function, and it is constant for any given material. As a result, the equation is as follows:
K.E. = hν – Φ …(2)
Einstein's photoelectric equation is as follows.
The photoelectrons are in the same situation. Electrons must have certain threshold energy to be expelled off the surface. When electrons are given a threshold frequency (v0), they gain enough energy to escape off the surface. If the electron receives energy equal to the threshold frequency, its kinetic energy is zero after exiting the surface. We've used this before.
hv0 – Φ = 0 or hv₀ = Φ ….(3)
Using equation (2), K.E. = hν – hν₀
Or K.E. = h(ν – v₀)
Also, v0 = Stopping Potential
K.E. (max) = eV₀
putting this with equation (3), we get:
eV0 = h (ν – v₀) ……(4)
The value of 'h' for the Photoelectric effect is derived using this equation. The numbers produced by this equation correspond to real values, validating Einstein's explanation for the Photoelectric effect.