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Electromagnetic Waves: Definition, Equation, Characteristics and Applications

Electromagnetic waves can also be termed EM waves. EM radiations use EM waves which can be generated when an electric field contacts the magnetic one. The natural characteristic of electromagnetic waves is nothing but their frequency. Maxwell explains that the electric field can be significantly raised by changing the magnetic field. Due to the acceleration of charges, there produced a time-varying magnetic field, which acts as a major component in generating a time-varying electric field. Therefore, electromagnetic waves contain a time-varying magnetic and electric field which is sinusoidal in nature. Both of these fields act perpendicular to one another.

Characteristics of electromagnetic waves

Electromagnetic waves have enormous amounts of characteristics. Some of the most important ones are mentioned below,

  • These waves are transverse in nature. They can be propagated by changing the electric and magnetic fields which are kept perpendicular to one another.
  • Electromagnetic waves are produced with the aid of accelerated charges.
  • These waves contain constant velocity in a vacuum. This can be almost equal to 3*108 m s-1. This can be indicated by the following equation, 
  • In order to propagate, these waves do not need any medium to travel.
  • The frequencies of the electromagnetic waves are not changed. However, the wavelength of these waves changes whenever travel happens between one medium and another.
  • A material’s refractive index is provided by, 
  • These waves strictly follow the principle of superposition.
  • The reason for the occurrence of optical effects due to electromagnetic waves is because of the light vector. Light vector can also be determined as an electric vector.
  • In an electromagnetic wave, both the electric and magnetic fields are in an oscillating manner and are contained in the same phase. The magnitudes of these electric and magnetic fields possess a constant ratio.
  • The ratio of the electric and magnetic field’s amplitude is equivalent to that of the velocity of the electromagnetic wave. This can be expressed as follows, 
  • The energy which is being carried by the electric field and magnetic field contained in the electromagnetic field are the same. In simple words, electric energy (uE) is equal to magnetic energy (uM). This can be expressed as follows, 
  • The energy transformation using electromagnetic waves per second per unit area can be simply represented by a vector quantity S. This is known as the Poynting vector. The expression of this vector is as follows, 

Electromagnetic wave equation

This equation describes the transmission of waves in a vacuum or through a medium.

The electromagnetic wave equation is considered a 2nd order fractional differential equation.

It is known as a three-dimensional form of the wave equation.

The following is the standardized way of expressing the equation, 



  • Likewise, given below is the equation for electromagnetic wave intensity, 
  • The expression given below is for the speed of electromagnetic waves in free space, 

Where, 0 is known as absolute permeability. The value of absolute permeability is


is known as absolute permittivity. The value of absolute permittivity is 


C acts as the velocity of light in vacuum. The velocity of electromagnetic waves in free space is given by, 3*108 m s-1.

Electromagnetic spectrum

Electromagnetic waves

There are two ways in which an electromagnetic wave is classified. One is based on the frequency f and the other one is based on its wavelength, which is


The following are the wavelength ranges of various lights,

  • Wavelength range for red light would be approximately around 700 nm.
  • Wavelength range for violet light would approximately be around 400 nm.
  • Wavelength range for visible light is approximately between 400 nm and 700 nm.

Applications of electromagnetic waves

Electromagnetic waves can be used in many domains due to their versatile nature. The following are some of the most common ones,

  • RADAR technology uses electromagnetic waves.
  • There are multiple ways an electromagnetic wave can be utilized in communication technology, as it helps transmit signals from one source to another.
  • These radiations are capable of transmitting energy in a vacuum or without using any medium at all.
  • Ultraviolet rays can simply be utilized to detect banknotes and check if they are forged or not. The banknotes which are original do not turn fluorescent under the UV light.
  • Due to the ability of infrared radiation to be visible under night vision, it can be used in security cameras.





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