Nature of Electromagnetic Waves

Electromagnetic waves are the form of visible light that enables us to view the world around us. There are various electromagnetic waves such as infrared rays, microwaves, gamma rays, ultraviolet rays, etc. Every wave has a distinctive characteristic, a range of specific frequency and wavelength; hence, it is used in different realms. 

Maxwell was the first scientist to predict the presence of electromagnetic waves. These waves were detected by Hertz. Another scientist called JC Bose created an electromagnetic range of wavelengths from 5 to 25 millimetres. Macaroni did a successful transmission of electromagnetic waves up to a few kilometres.

Now let’s delve into the study material and notes on the nature of electromagnetic waves.

Nature of electromagnetic waves

The electromagnetic force is a force experienced by a charge or multiple charges placed in an electric or magnetic field due to interaction with each other. In 1870, Clerk Maxwell gave this term to explain the interaction between charges when placed in an electric or magnetic field. According to him, electrical and magnetic fields are transmitted and produced by accelerating the electrically charged particles; these fields cross in waves. These waves are defined as electromagnetic waves. Light waves are also electromagnetic waves.

Particle nature of an electromagnetic wave

Electromagnetic waves are packets of energies called photons. The energy associated with these photons is directly proportional to the frequency of electromagnetic waves. It can be better depicted by the formula E = hf, where h is Planck’s constant, E is the electromagnetic wave, and f stands for the frequency. We will discuss Planck’s constant in detail, but first, let us know more about these electromagnetic waves.

Electromagnetic waves travel or propagate in a direction mainly oriented at right angles to the vibrations of both the electrical (E) and magnetic (B) oscillating field vectors, transporting energy from the wave source to an undetermined final destination. The energy fields that are in oscillation are perpendicular to each other. Electric field vectors seem to be perpendicular to each other and perpendicular to the direction of wave propagation. 

Electromagnetic waves and their properties

• Electromagnetic waves can travel in any medium.

• Electromagnetic waves differ according to their wavelengths and frequencies. If you consider the electromagnetic wave as a whole, it makes up the electromagnetic spectrum. For example, you can refer to the ultraviolet region, visible region, radiofrequency region, etc.

• The oscillating charged particles produce oscillating electric and magnetic fields, which are perpendicular to each other. These charged particles are also oscillating perpendicular to the direction of wave propagation.

• An electromagnetic wave is also specified, depending on various properties. They are frequency, period, wavelengths, etc.

The formula of electromagnetic wave

There is a formula to calculate the frequency and wavelength of electromagnetic waves. The frequency of an electromagnetic wave is the number of waves that pass through a specific point in a second. The frequency of an electromagnetic wave is inversely proportional to its time. The equation to relate frequency, wavelength, and speed of light of electromagnetic wave is as follows:

                c = v × λ

Where c is the speed of light, v is the frequency of the electromagnetic wave, and lambda (λ) refers to the wavelength of the electromagnetic wave.

One can also determine electromagnetic waves by other parameters like wave numbers. Simply put, wave numbers are the number of wavelengths per unit length; they are inversely proportional to the wavelength of electromagnetic waves.

Dual behaviour of electromagnetic wave

Since electromagnetic waves exist both in wave nature and particulate nature, it is known to show dual behaviour. 

Electromagnetic waves can be defined as spectrums that consist of infrared waves, ultraviolet waves, microwaves, and gamma rays. Energy transfer from one place to another can only become possible in two ways—through waves and through particles.

To explain the photoelectric effect of electromagnetic waves, you need to know that they consist of energy packets called photons. From the photoelectric effect of electromagnetic waves, it is clear that they possess a wave nature of the electromagnetic wave, and hence we can conclude that electromagnetic waves are dual. 

Planck’s quantum theory

Two points can explain this theory of electromagnetic waves.

1. The frequency of electromagnetic waves is equal to the energy of absorbed or emitted waves.

2. The atoms and molecules can emit and absorb a specific quantity of energy. The smallest amount of energy absorbed or emitted is termed quantum.

According to Planck’s quantum theory, 

 E= hv

Here, h is Planck’s constant, and its value is 6.626×10-34 J.s.

All electromagnetic waves behave according to wave theory or quantum theory. Electromagnetic waves consist of an electric field that varies in a direction perpendicular to the direction of propagation of the wave and a magnetic field that is set at right angles to the electric field.

Both electric and magnetic fields travel at the speed of light. To understand remote sensing of electromagnetic waves, you need to know the two main characteristics and their wavelength and frequency.

Conclusion

The primary difference between various electromagnetic waves lies in their wavelengths or frequencies. Consequently, the waves differ considerably in their mode of interaction with the matter. Infrared waves with frequencies lower than that of visible light vibrate not only the electrons but the entire molecule or atom of a substance. This vibration increases the internal energy and hence the temperature of that particular substance. This is why these waves are called heat waves. The centre of sensitivity to our eyes coincides with the centre of the wavelength distribution of the Sun. Humans evolved with vision most sensitive to the visible region of electromagnetic waves from the sun.

These electromagnetic waves are responsible for many scientific developments which we see today and have been a major part of our lives, as they have many practical implications.