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Is light wave or a particle? And Who discovered the photoelectric effect?

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Who discovered the photoelectric effect? The light is a form of energy that can be transferred from one point to another either by particle motion or by wave motion. Accordingly, different theories on the nature of light have been proposed. Some of the important theories are explained here

Newton’s corpuscular theory

The earliest theory to explain the properties of light is Newton’s corpuscular theory proposed by Sir Issac Newton in 1678. According to this theory, light consists of small particles called corpuscles.

Huygen’s Wave theory

According to this theory, every point of a luminous body acts as a source of disturbance. The disturbance is due to the vibrations of the atoms and molecules of the source of light and the disturbance travels in the form of longitudinal waves in an ether medium.

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Maxwell’s electromagnetic theory

Electromagnetic theory is proposed by James Clerk Maxwell. According to this theory, light is an electromagnetic wave. The electromagnetic waves are transverse in nature. The existence of electromagnetic waves was proved experimentally by Hertz in the year 1888.

Planck’s Quantum theory of radiation

The photoelectric effect and the energy distribution in the black body could not be explained by electromagnetic theory. Max Planck put forth the revolutionary quantum theory. This theory explained the black body radiation. The theory was later used by Einstein to explain photoelectric effect. According to quantum theory of radiation emission or absorption take place in discrete amounts called quanta. Einstein called these quanta as photons.

Dual Nature of Light

Is light wave or a particle? To explain the properties of light such as interference, diffraction, polarisation the wave aspect of light is considered. To explain the phenomenon like photoelectric, process of emission,absorption and scattering one should consider the particle nature of the light. Therefore, it was concluded that light has a dual nature. The de Brogle hypothesis on matter waves is a confirmation of the dual nature of light.

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Who discovered photoelectric effect?

The emission of photons from the surface of the metal plate when it is illuminated by light of suitable frequency is called photoelectric effect. Who discovered photoelectric effect? The phenomenon of photoelectric effect was first observed by Heinrich Hertz in the year 1887. In his experiment he saw that electric charge was given out from the cathode when it was illuminated by ultraviolet rays. He did not research further on this. The work on photoelectric effect was later done by J.J. Thompson. He found out that electrons were ejected when metal plates are illuminated by ultraviolet rays. The same phenomenon was later explained by Einstein. Einstein said light is made up of small particles called photons. When these photons present in the light hit the electrons in the metal, it gives the electrons enough energy to escape from the metal surface.

The electrons released from the metal surface are called photoelectrons. The current that is getting generated during the photoelectric effect is called photocurrent. The maximum value of the photocurrent is called the saturation current.

 

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