Photoelectric Emission- Definition, Working, Methods, Uses & Applications

Define Photoelectric Emission?

What is Photoelectric Emission?

The cycle by which free electrons are emitted from the metal surface by the utilization of light is called photoelectric emission.

It is also defined as, the interaction by which free electrons are released from the metal when it ingests light energy. Photoelectric emission is likewise called as photoemission or photoelectron emission or photoelectric effect.

In this method, light or photons is utilized to eliminate the free electrons from the solid metal. Subsequently, the free electrons emitted from the strong metal are called photoelectrons and current produced because of this interaction is called photoelectric current.

Metals without light energy

Whenever the light energy isn’t applied to the metals, the free electrons can’t escape from the metals. In any case, some of the valence electrons become free from the atoms.

At ordinary temperature, some valence electrons get sufficient energy from the heat source. The valence electrons, which gets adequate energy will breaks the holding with the parent atom and turns out to be free.

The free electrons, what breaks the holding the parent atom, have some kinetic energy. In this way, they move freely from one point to another point. However, they need more energy to turn out to be liberated from the metal. The solid attractive force of the nuclei prevents the free electrons, which attempt to escape from the metal.

To conquer the attractive force of the nuclei, the free electrons need adequate energy from the light. The free electrons, what break the holding with metal, will moves into the vacuum.

Photons and its effect on metals

Photons are the smallest particles of light. Unlike electrons and protons, photons have no mass. However, photons have energy.

Visible light and any remaining types of light like radio waves, microwaves, infrared light, bright light, X-rays, and gamma rays are comprised of photons. However, the energy of photons isn’t same for all these lights. For instance, gamma rays (photons) have more energy than the infrared light (photons). The energy of photons is relies upon its frequency, though the intensity of light is depends upon the number of photons.

Whenever the light energy is applied to the metal, the free electrons acquires energy. In other words, when the light particles (photons) hits free electrons in the metal, they move their energy to the free electrons. The free electrons, which acquires additional energy from the light, will attempt to the beat the attractive force of the nuclei.

Assuming the light energy applied to the metal is additionally expanded to a higher value, the free electrons in the metals gain adequate energy and defeat the strong attractive force of the nuclei. The free electrons, which defeat the strong attractive force of the nuclei, will jumps into the vacuum.

Note: Photoelectric emission relies or depends upon the frequency of light and doesn’t depends the intensity of light

Frequency of light

The energy of photons is relies upon its frequency. Photons with low frequency have low energy though photons with high frequency have high energy. High-energy photons or high frequency photons are needed to emit the free electrons from the metals.

At the point when the high-energy photons are applied to the metals, free electrons are gotten away from the metal surface. The minimum energy or the minimum frequency that the photons expected to eliminate the free electrons from the metals is called threshold frequency or threshold energy of photons. This threshold frequency isn’t same for all metals. It is different for various metals.

Assuming the light energy applied to a metal reaches or surpasses the threshold frequency, it begins emitting the free electrons. Then again, assuming that the light energy applied to a metal is below the threshold frequency, it doesn’t emit the free electrons.

Intensity of light

The quantity of photons strikes the free electrons in the metal relies or depends upon the intensity of light. Low intensity light has less number of photons. Henceforth, on the off chance that low intensity light is applied to the metal, less number of photons strikes the free electrons in the metal.

Then again, high intensity light has more number of photons. Henceforth, if high intensity light is applied to the metal, more number of photons strikes the free electrons in the metal.

High frequency and low intensity light

If high frequency and low intensity light is applied to the metal, less number of photons hits the free electrons in the metals. In any case, every individual photon, which hit the free electron, has energy or frequency greater than the threshold frequency or threshold energy.

Hence, every individual photon gives sufficient energy to the free electron to escape from the metal. In this manner the free electrons emitted from the metal surface is relies or depends upon the frequency of light.

Low frequency and high intensity light

If low frequency and high intensity light is applied to the metal, more number of photons hits the free electrons in the metals. However, every individual photon, which hits the free electron, has energy or frequency less than the threshold frequency or threshold energy.

Hence, every individual photon doesn’t give sufficient energy to the free electron to escape from the metal. A single electron absorbs energy from a single photon. They can’t absorb energy from more than one photon to escape from the metal. Thus, the free electrons emitted from the metals don’t rely upon the intensity of light.

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