The universe looked to be a simple and orderly place, including matter, which consisted of:

  • Mass-bearing particles whose location and motion could be precisely defined
  • Electromagnetic radiation was thought to have no mass and whose precise position in space could not be determined.

As a result, matter and energy were considered separate and unconnected things. The various theories that various scientists at that time devised are mentioned below:

 

In 1900, Max Planck, a renowned German physicist, discovered that some types of metals emitted free electrons when they came into contact with light. The photoelectric effect was properly addressed in this experiment. Following up on this experiment, Albert Einstein established the particle nature of light. He claimed that electromagnetic energy is distributed in packets or quanta, commonly known as ‘photons.’

According to previous measurements, the wavelength of light had a significant impact on the expelled electrons. In addition, the amount of light emitted has a direct impact on the electrons released. This fact revealed the particle nature of light, which had previously been thought to be a wave by physicists.

Some of the characteristics of light are:

  • It can act as a particle (known as a photon) as it travels in straight lines. 
  • It can function as a wave, explaining its bending or diffraction around any object at a time. 
  • Light has interference capabilities, as observed in the development of dark and brilliant fringes in Young’s Double Slit Experiment.
  •  Natural skylight is partially polarised; however, it can be completely polarised after passing it through a polaroid.

Photon

A photon may be a particle of sunlight or any light defined as a discrete bundle (or quantum) of electromagnetic (or light) energy. 

Photons are always in motion, even when in a vacuum. They always have a spontaneous speed of light within them. Photons travel at the speed of light in vacuum(more commonly just called the speed of light) of c = 2.998 x 108 m/s. Gilbert Lewis coined the term photon in 1926. Although the concept of particles being present in light has been around for more than a decade or so. 

Basic Properties of Photons

According to the photon theory of light:

  • Photons carry energy and momentum, which are also related to the frequency and wavelength of the electromagnetic wave.
  • Photons can be eliminated or created when radiation is absorbed or emitted.
  • Photons can have particle-like collisions with electrons and other particles, as in the Compton effect, when light particles are hit with atoms and cause electrons to be released.

Features of Photons Picture of Electromagnetic Radiation

The photon’s picture of electromagnetic radiation are as follows: 

  • Photons are light particles with the energy E = hv and momentum p = h/λ, where h is the Planck constant.
  • In a vacuum, photons travel at the speed of light, regardless of the frame of reference.
  • The number of photons crossing a unit area in a unit time determines the light intensity.
  •  There is energy hv in each quantum of radiation. 
  •  The photoelectric effect causes the metal’s electrons to absorb this quantum of energy (hv). The flow of photo-current begins when this energy exceeds the minimum energy required for photo-electron ejection. 

Photon-particle collision

When a high-energy photon collides with the matter, it frequently transforms into an electron-positron pair, which entails that the massless photon’s energy is transferred into the pair’s masses.

A comparable reaction occurs when heavy ions are crushed together at high energies at facilities like the LHC. These ions are surrounded by clouds of photons, which can form pairs of particles when they collide with one another.

CERN’s Compact Muon Solenoid (CMS) group has devised a new method to analyse matter generated during the collision of photons. While the team’s findings align with the Standard Model of particle physics, they hope that additional observations may lead to findings that will challenge our current understanding of physics.

Light

The sense of sight aids our perception of the world around us. The light from the sun lets us view our surroundings during the day, while the light from the moon lights up our environment at night. As a result, we require a source of light to see. 

The electromagnetic radiation that the human eye can recognise is light. Electromagnetic radiation has a wide range of wavelengths. The wavelengths visible to humans comprise a reasonably narrow region within that large spectrum.

Conclusion

This article walked you through the various aspects of light and its nature. Light has a dual nature. It has both particle nature as well as electromagnetic nature. The particle nature states that the light has several packets of light known as photons. In 1900, Max Planck, a renowned German physicist, discovered that some types of metals emitted free electrons when they came into contact with light. The photoelectric effect was properly addressed in this experiment. Following up on this experiment, Albert Einstein established the particle nature of light. He claimed that electromagnetic energy is distributed in packets or quanta, commonly known as ‘photons.’ Photons can be eliminated or created when radiation is absorbed or emitted.