Photon

A photon is a type of tiny particle composed of various waves of electromagnetic radiation. Maxwell, in an experiment, found out that photons are simple electric fields that travel through space, have particularly no charge or resting mass and mainly travel at the speed of light.

Photons are mainly emitted through charged particle actions, besides the use of other methods like radioactive decay. As photons are quite small, they contribute towards wavelike characteristics, and the behaviour of photons is significant. 

What are Photons?

Photons are also known as energy packets. The energy contained in photons cannot be divided. Hence the energy is stored in a particular oscillating field. The oscillation of the fields happens at any frequency. It is said that the shortest possible length of a photon is that of Planck length.

Photons can be transmitted at vast distances as there has been no decay related to energy or speed. Photons generally travel at a speed of light that is 2.997 x 108 m/s in a space. The speed of a photon through space is derived directly from the speed of an electric field through free space. It was Maxwell who discovered it in 1864.

Though photons don’t have a mass, or we can say the mass of a Photon is 0, they possess a momentum that follows the equation of De Broglie. 

It is also important to note that photons have similar properties to electromagnetic waves. For example, every photon possesses a wavelength as well as frequency. Wavelength is defined as the distance between the two peaks of the electric field with that of the same vector. On the other hand, the frequency defines how many wavelengths a photon can propagate with each second.

However, it possesses an important difference from electromagnetic waves, i.e., the photon does not possess a colour, but it corresponds to the light of a colour. This is because the human eye’s capabilities define the colour of an object; since photons cannot be seen with the naked eye, they don’t possess a colour. Therefore, for the retina to recognize the photon’s colour, various photons are required to act on it. Only when photons act with each other on the retina in the form of electromagnetic waves can the colour be perceived.

Equations of Maxwell

Photons are well described with the help of the equations provided by Maxwell. The equations given by Maxwell predict how photons can move through space. Essentially an electric field undergoes a flux that creates an orthogonal magnetic field. The flux of this magnetic field recreates an electric field. Thus, the creation and the destruction of each of the corresponding waves allow the pair of waves to move at the speed of light. Therefore the equations by Maxwell essentially describe the nature of the individual photons within a proper framework of quantum dynamics. 

The Creation of Photons

Photons can be generated in various ways. We will discuss some of the ways through which photons can be emitted.

1.The Blackbody Radiation

 As a substance gets heated, the atoms within it vibrate at a higher energy. These vibrations quite frequently change the shape and energies of the electron orbitals. Since the energy of the electron changes, photons are emitted and absorbed at energies corresponding to the changed energy. With the phenomenon of blackbody radiation, the light bulb glows, and the object’s heat is felt from a long distance.

2.Fluorescence

Fluorescence is a type of spontaneous emission. In fluorescence, essentially, the photon’s energy does not match the energy that excites the electron. An electron only will fluoresce when it loses a significant amount of energy to its environment before it undergoes a relaxation. Now essentially, fluorescence is used in a laboratory setting to visualise the target molecule’s presence. The UV light excites electrons; hence, when it emits light at specific visible wavelengths, scientists can see it.

3.Spontaneous Emission of Photons

Another phenomenon that leads to the release of photons is when the electrons fall from an excited or a higher state to a lower energy state. Now the drop in the energy is termed relaxation. The electrons undergo this emission type, producing a set of distinctive photons based on the energy available in the environment. This is also the basis for the emission spectrum.

4.Stimulated Emission

An excited electron can be artificially relaxed to a lower state of energy with a matching photon. The phase of the electric field and the orientation of the photon that is resultant, along with its energy and direction, will be identical to that of the incident photon. The light produced through stimulated emission is said to be similar to the photon that causes the emission. Lasers produce electromagnetic radiation that is coherent with the help of stimulated emissions.

5.Synchrotrons (Electron Bending)

Electrons that possess high kinetic energy produce high energy photons when the path gets altered. This alteration is coupled with a magnetic field that is highly strong. All types of free electrons emit light in a particular manner; however, synchrotron radiation has various special applications. For example, this technology is currently used for x-ray applications to provide radiation at specific frequencies. 

What is the Photoelectric Effect?

The incident ray of light on a metal plate causes several electrons to break loose from the surface. The interaction that occurs between light and electrons is known as the photoelectric effect. This photoelectric effect provides the first evidence that beams of lights are made of quantized particles. Einstein later explained this theory, which stated that light is made up of quantized packets of energy called photons.

Conclusion

Maxwell, in an experiment, found out that photons are simple electric fields that travel through space, have particularly no charge or resting mass and mainly travel at the speed of light. Photons are mainly emitted through charged particle actions, besides the use of other methods like radioactive decay. As photons are quite small, they contribute towards wavelike characteristics, and the behaviour of photons is significant.