Laws Of Photoelectric Effect

The following are the laws of photoelectric emission:

• The velocity of released electrons is unaffected by light intensity and is solely determined by the frequency (or wavelength) of the incident light.
• Photoelectric current (or photoelectrons expelled per second) is proportional to incident light intensity.
• There is a minimum frequency below which the emission of electrons stops completely for a specific metal. The threshold frequency is the frequency at which something happens.
• Photoelectric emission is a one-time event.

 Photoelectric Effect

When a substance absorbs electromagnetic radiation, electrically charged particles are emitted within or from it. This is known as the photoelectric effect. The ejection of electrons from a metal plate when light shines on it is called photoelectric  effect. This phenomenon has been shown to be advantageous in electronic devices that are designed to detect light.

When metals are exposed to light of the suitable frequency, the photoelectric effect occurs, and the electrons emitted are termed as photoelectrons.

Laws of Photoelectric Effect

• For every given frequency of light, the photoelectric current is proportional to the intensity of light; ( γ> γ Th).
• The discharge of photoelectrons stops completely below a particular minimum (energy) frequency for a certain material, known as the threshold frequency, regardless of the intensity of input light.
• The photoelectrons’ maximum kinetic energy rises as the frequency of the incident light rises (assuming frequency γ> γ Th exceeds the threshold limit). The maximum kinetic energy is independent of light intensity.
• Photo-emission is a phenomenon that occurs in a split second.

Photoelectric Effect: Concept of Photons

Instead of thinking of light as a wave, we should think of it as a stream of particles (i.e., electromagnetic energy). As a result, these light ‘particles’ are referred to as Photons. The energy stored by photons is proportional to the frequency of light, according to Max Planck’s equation.

It can be expressed as:

 E=hν=hc/λ

HereE = energy of photon

 h = planck’s constant

  = frequency of light

 c = speed of light and

  = wavelength of light

Properties of Photon

• A photon’s quantum number is zero.
• There is no mass or charge in a photon.
• An electric field and a magnetic field do not reflect photons.
• The speed at which a photon passes through empty space.
• The energy of photons is related to their frequency.
• The energy of a photon is inversely proportional to the wavelength of a proton.

Maximum kinetic energy

The maximum kinetic energy of photoelectric effect is given as :

 E=hc/λ-W

The gap between the energy of the incident photon and the work function of the metal determines a photoelectron’s maximum kinetic energy at a metal surface. The binding energy of electrons to the metal surface is referred to as the work function.

photoelectric emission

• Photoelectric emission is the process of free electrons being emitted from a metal surface when light is applied.
• The method by which free electrons are released from a metal when it absorbs light energy is also defined. Photoemission, photoelectron emission, and photoelectric effect are all terms used to describe photoelectric emission.
• Light, or photons, are utilised to extract free electrons from a solid metal in this approach. As a result, photoelectrons are free electrons emitted from a solid metal, and photoelectric current is the current created as a result of this process.

Metals without light energy

The free electrons cannot escape from metals when light energy is not provided to them. Some of the valence electrons do, however, break out from the atoms.

Some valence electrons obtain enough energy from the heat source at room temperature. When the valence electrons have enough energy, they will break the bond with the parent atom and go free.

The free electrons, which are responsible for breaking the link between the parent atom and the child atom, contain kinetic energy. As a result, they can easily migrate from one spot to another. They don’t have enough energy, though, to break free from the metal. Free electrons attempting to escape from the metal are prevented by the strong attracting force of the nuclei.

The liberated electrons require enough energy from light to overcome the nuclei attracting pull. The liberated electrons will travel into the vacuum after breaking their link with the metal.

Photons and its effect on metals

The smallest particles of light are called photons. Photons, unlike electrons and protons, have no mass. Photons, on the other hand, have energy.

Photons make up visible light and all other types of light, including radio waves, microwaves, infrared light, ultraviolet light, X-rays, and gamma rays. The energy of photons, on the other hand, is not the same for all of these lights. Gamma rays (photons), for example, have greater energy than infrared light (photons). The frequency of photons determines their energy, whereas the quantity of photons determines the intensity of light.

The free electrons gain energy when light energy is imparted to the metal. In other words, when light particles (photons) collide with free electrons in metal, their energy is transferred to the free electrons. The liberated electrons will strive to overcome the nuclei attracting force by gaining extra energy from the light.

Conclusion

A photon is a unit of light that is made up of constituent particles. Photons are energy packets with a certain amount of motion, but their rest mass is zero. We discovered that as the intensity of light increases, the photoelectron’s maximum kinetic energy remains constant, while the photocurrent value increases. For a given metal, the photoelectron’s maximum kinetic energy is solely determined by the incident light’s frequency. The work function is the amount of work that must be done in order for a metal to emit a photoelectron. It is determined by the metal. The threshold frequency is the frequency of light that is just enough to emit a photoelectron, i.e. the photoelectron’s kinetic energy is zero.