Particle Nature of Light-Photoelectric Effect

The particle nature of light was discovered by Albert Einstein. According to him, electromagnetic energy comes in quanta or packets and it is also known as ‘photons’. Earlier, physicians were of the opinion that light can proceed like a wave. But the experiment based on the photoelectric effect stated that the photoelectric effect also consists of energy packets. The wave nature of light means that light can behave as an electromagnetic wave. On the other hand, the particle nature of light means the light comprising of

particles and it is known as photons. In quantum mechanics, wave-particle duality

and photons are important chapters. The dual nature of matter and the particle

 nature of light is comparatively a discovery. A matter can have a wave nature

or particle nature. To prove the particle nature of matter theory various experiments were conducted later.

Important concepts of Particle Nature of Light

A few necessary topics regarding this concept are the following:

• Photon’s energy always depends on its wavelength. The photons having longer wavelengths always have less energy, whereas shorter wavelength photons have more energy. For example, Red Photons have less energy than Blue Photons.
• The more energetic wavelength for instance Blue and Ultraviolet Photons causes more electrons in comparison with Red Photons. Physicists also discovered that as the light intensity increases and more the electrons ejected ,the photons speed will not increase.
• According to a Physicist, named Planck, the radiation of electromagnetic energy was proportional to its frequency. 

What is the Photoelectric Effect?

The photoelectric effect phenomenon requires electrons that can escape from the material’s surface. This material surface consists of both positive ions as well as negative ions. As the metal surface is hit by the light,  few electrons absorb energy from the radiation of the incident and gradually overcome the positive ions attraction. After that, the electrons got enough energy to escape out of the surface of the metal. This process is known as the photoelectric effect.

Few facts and terms related to the photoelectric effect:

• Threshold Frequency: Threshold frequency of light is maximum that forces a photoelectron to emit from a metal surface.

•  Work Function: Work function is the minimum energy and it is required to eject an electron from a metal’s surface.

• Threshold Wavelength: Threshold wavelength  is known as the maximum wavelength of light that ejects a photoelectron from the metal’s surface.

• The cut-off is the retarding potential or minimum negative that is denoted by V0, where the value of photoelectric current will become zero. This is also known as stopping potential.

•  The incident light intensity effect falling is direct with the photoelectric current for a fixed frequency of incident.

Photoelectric Effect: Laws

The laws associated with the Photoelectric effect is discussed below:

• The Photoelectric effect is directly proportional to the incident power of the light on a given metal surface and it is also the incident light frequency.
• The frequency threshold exists for a specified metal. In this definite least frequency the photo-electric emission is absent.
• The maximum kinetic energy level of the photoelectrons is dependent on the incident light frequency.
• The photoelectric process is instantaneous.

Different Theories on the Dual Nature of Matter

De Broglie Hypothesis

In the De Broglie hypothesis, he defined the relation between wavelength and momentum.

Planck’s Quantum Theory

This theory explains that when we apply heat to a black body, this will lead to thermal radiation emission with various frequencies or wavelengths.

An Experiment conducted by Davisson and Germer 

This experiment proves the electron’s wave nature and also verifies the equation of de Broglie.Later,  it resulted in establishing the first proof based on an experiment on quantum mechanics. The parts that are involved in this experiment are the following:

Electrostatic Particle Accelerator: To accelerate the electrons two contradictory charged plates are needed to be employed and this process is called potential.

Electron Gun: This is a Tungsten filament emitting electrons through thermionic emission.

Collimator: The accelerator that has a narrow beam is tied within a cylinder for the electron together with its axis.

Target: Target is a Ni crystal where the beam of the electron is ejected. To catch the electrons that are separated from the Ni crystal, detectors are used.

Conclusion

On a concluding note, in this article, we have learned about the concept of the particle nature of light and a few important concepts related to this topic. The main difference between the wave nature of light and the particle nature of light is that the wave nature of light means that light can behave as an electromagnetic wave. On the other hand, the particle nature of light means the light composed of particles also known as photons.  Along with this in this article, we have also learned about the concept of the photoelectric effect and a few facts and terms related to the photoelectric effect.