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# Electromagnetic Waves

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 Sub Topics Waves are ubiquitous in nature. We are familiar with many of their physical properties from our every experience. Main types of waves are mechanical waves and electromagnetic waves.Visible light is an example of electromagnetic wave, as are the radio and television signals we increasingly rely on in our information technology age. Energy transfer in vacuum is possible through the electromagnetic waves. Because they can travel with out any medium. Definition, properties, types and applications of electromagnetic waves are mentioned in below section.

## Definition

Electromagnetic waves are generated due to the combined action of electric and magnetic fields. This electric and magnetic waves are perpendicular to each other, these are perpendicular to the direction of propagation also. Electromagnetic waves can travel through vacuum.The main difference between electromagnetic waves and mechanical waves are electromagnetic waves can travel through vacuum and it can be radiative in nature whereas the mechanical waves cannot travel through vacuum, it needs a medium to propagate and these are not radiative waves.

## Types

Electromagnetic waves have both electric and magnetic components. They are classified according to their wavelengths, that is the distance between two waves. The range of electromagnetic waves is known as the electromagnetic spectrum. For the study, the electromagnetic spectrum is divided into eight major regions:

All of these waves, with the single exception of visible light, are invisible to the naked eye.

## Properties

An early result of Maxwell's theory was the prediction and later verification by Heinrich Hertz of the existence of electromagnetic waves. We know that nearly any time varying source produces waves and that these waves have certain important properties. An electromagnetic wave is a propagating electromagnetic field that travels with finite velocity as a disturbance through a medium. The field itself is the disturbance, rather than merely representing a physical displacement or other effect on the medium. This fact is fundamental for understanding how electromagnetic waves can travel through a true vacuum. Many specific characteristics of the wave such as velocity and polarization depend on the properties of the medium through which it propagates. The evolution of the disturbance also depends on these properties: we say that a material exhibits "dispersion" if the disturbance undergoes a change in its temporal behavior as the wave progresses. As waves travel they carry energy and momentum away from their source. This may be later returned to the source or delivered to some distant location. Waves are also capable of transferring energy to, or withdrawing energy from, the medium through which they propagate. When energy is carried outward from the source never to return, we refer to the process as 'electromagnetic radiation'. The effect of radiated fields can be far-reaching; indeed, radio astronomers observe waves that originated at the very edges of the universe. Radio waves bend in the ionosphere much as light waves bend while passing through a prism. Microwaves reflect from conducting surfaces in the same way that light waves reflect from mirror; detecting these reflections forms the basis of radar.

## Electromagnetic Wave Spectrum

Electromagnetic spectrum can be classified according to the wavelength or frequency of electromagnetic waves. The electromagnetic spectrum of em wave is given below:

## Speed of Electromagnetic Waves

The peculiarity of electromagnetic waves is it can be travel through vacuum as well as through a medium. But the velocity is different in vacuum and medium. In vacuum em waves travels in the speed of light, that is, 3$\times10^{8}$ m/s. The speed is different in medium according to their refractive index.

## Energy in Electromagnetic Waves

By the means of electromagnetic waves, an energy can be transported from transmitter to receiver. The energy stored in an electric and magnetic field is transmitted at a certain rate of energy flow which can be calculated with the help of poynting theorem.

## Characteristics

Some of the important characteristics of electromagnetic waves are listed below:
• In vacuum, the velocity of the em wave is same as of light in vacuum
• Medium is not compulsory for propagation of em waves
• It can be polarized like light
• These waves comes under transverse type
• These are unaffected by electric or magnetic fields
• These waves show interference and diffraction like light

## Are Electromagnetic Waves Transverse?

Yes, electromagnetic waves are transverse in nature. Electromagnetic waves are generated due to the effect of both electric and magnetic fields. These are perpendicular to each other. And the propagation direction is also perpendicular to it. So we can say that it is transverse in nature.

## Do Electromagnetic Waves Need a Medium?

The Medium is not compulsory for an electromagnetic wave for propagation. It can be travel with or without medium. But the speed is vary according to the behavior of the medium. Speed is high at vacuum, and it differ for different medium since their refractive index is also different.

## Is Sound an Electromagnetic Wave?

No. Sound is not an electromagnetic wave. Sound is a mechanical wave. A medium is necessary for a sound to propagate from one place to other. The one of the difference between electromagnetic wave and mechanical wave is that, em wave can propagate even in the absence of medium, but a mechanical wave can't.