Introduction

To comprehend the propagation of electromagnetic waves, it is necessary first to comprehend what an electromagnetic wave is. Vibrations between an electric field and a magnetic field cause electromagnetic waves to be produced. The speed at which electromagnetic waves propagate in the vacuum is 3*108m/s, and the speed at which electromagnetic waves propagate through any medium is less than the speed in the vacuum. A discharging spark or an oscillating molecular dipole are two examples of generating electromagnetic waves. The amplitudes and directions of oscillating electric and magnetic fields are represented by vectors that undulate in two mutually perpendicular planes as sinusoidal waves in visible light, which is a commonly studied kind of electromagnetic radiation. The oscillations or vibrations that cause electromagnetic radiation are known as electromagnetic waves. The oscillation of an electric field, the magnetic field, and the propagation of waves all have perpendicular directions. 

 The absorption and reemission of wave energy by the medium’s atoms is the mechanism of energy transmission via a medium. The energy of an electromagnetic wave is absorbed when it strikes the atoms of a material. The absorption of energy causes the vibrations of the electrons within the atoms. After a fast vibrational motion, the vibrating electrons form a new electromagnetic wave with the same frequency as the previous one. While these vibrations last only a fraction of a second, they slow the wave’s progress through the medium. When an atom emits the energy of an electromagnetic wave, it travels across a short region of space between atoms. The electromagnetic wave is absorbed and transformed into electron vibrations before being reemitted as an electromagnetic wave once it reaches the next atom. While the electromagnetic wave will travel at the speed of light in the vacuum of interatomic space, the net speed of the electromagnetic wave will be less than the speed of light due to absorption and reemission. The optical density of a material medium determines the actual speed of an electromagnetic wave passing through it. Different materials create varying amounts of delay because of the absorption and reemission process.

Furthermore, certain materials have more closely packed atoms, resulting in less gap between atoms. The type of substance the electromagnetic wave travels determines these two elements. As a result, the speed of an electromagnetic wave is determined by the substance it passes through. 

 Modes of propagation of electromagnetic waves

Following are the ways through which electromagnetic waves propagate from the transmitter antenna to the receiver antenna:

• Ground wave propagation is electromagnetic waves along the earth’s surface.
• The propagation of electromagnetic waves from the transmitter antenna to the receiver antenna without getting reflected from a surface or without refraction during the propagation of electromagnetic waves in a medium that propagation is known as space wave propagation. 
• The propagation of electromagnetic waves to the sky and then reflected earth from the ionosphere is skywave propagation.

Properties of electromagnetic waves

• The magnetic field and the pulsating electric field are in phase. 
• The velocity of the wave is equal to the ratio of the amplitudes of the electric and magnetic fields. They follow the formula c = f. Here, f denotes the frequency in Hertz, and m denotes the wavelength in meters. 
• The combination of wavelength and frequency equals a constant c, which is 3 x 108 m/s, the speed of light. We can deduce from this relationship between wavelength, frequency, and light speed that electromagnetic waves travel at the speed of light regardless of wavelength or frequency. 
• Electromagnetic waves are waves that are not mechanical. They don’t need any material to reproduce. Electromagnetic waves always move at a constant speed in a vacuum. 
• The waves are moving at 3 x 108 m/s. They propagate by altering electric and magnetic fields so that these two fields are at right angles to one another and the wave’s propagation path. 
• The nature of electromagnetic waves is that they are transverse. 
• Electromagnetic wave propagation in good conductors is not possible. We can define its velocity, frequency, and wavelength during electromagnetic propagation.

 Characteristics of electromagnetic waves

• Electromagnetic waves have a fundamental feature called frequency. 
• According to Maxwell, changing the electric field produces a magnetic field. A speeding charge produces a time-varying magnetic field, which in turn produces a time-varying electric field. 
• A sinusoidally oscillating electric and magnetic field perpendicular to each other makes up an electromagnetic wave. 
• Electromagnetic waves are transverse because they propagate by changing the electric and magnetic fields to be perpendicular to one another. Accelerated charges generate electromagnetic waves. There is no need for a material medium for electromagnetic waves to travel. 
• The frequency of an electromagnetic wave is a fundamental property. When a wave travels from one medium to another, its frequency remains the same, but its wavelength changes. 
• The principle of superposition governs electromagnetic waves. 
• The visual effects of an electromagnetic wave are caused by the light vector (also known as the electric vector). 
• The velocity of an electromagnetic wave is equal to the ratio of the amplitudes of electric and magnetic fields. 
• Electromagnetic waves’ electric and magnetic fields convey the same amount of energy, i.e. their electric and magnetic energies are equal. S, commonly known as the Poynting vector, is a vector quantity that indicates the amount of energy given per second per unit area by electromagnetic waves.

Conclusion

In this article, we read about the propagation of electromagnetic waves. We also read about the properties of electromagnetic waves, space wave propagation, and em wave propagation. This will help to learn clear concepts of electromagnetic waves.