electromagnetic waves - classification

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 electromagnetic waves

Introduction:


Different scientists put forwarded their concepts related to electro magnetic waves. some of them achieved success while others failed due to certain drawbacks. Faraday, a well known physicist concluded that a changing magnetic field produces an electric field. According to Maxwell , there is a great symmetry in nature that is a changing electric field should produce a magnetic field . Again Maxwell made his conclusion by saying that change in electric field and the magnetic field which are perpendicular to each other should produce electro magnetic disturbance in space. According to Maxwell, these electro magnetic disturbances have the properties of waves and hence these disturbances are also called electromagnetic waves or electromagnetic spectrum . 

According to Maxwell, if there is any variation in the electric field vector E and the magnetic field vector B, which are perpendicular to each other ,then electromagnetic waves are produced perpendicular to both E and B.

electromagnetic waves ,classification
electromagnetic waves - classification

electromagnetic waves 

According to Maxwell, the velocity of electromagnetic waves is given by :

                                      C = 1/√μ₀ε₀

where μ₀ is the permeability of free space  and  μ₀ = 4π× 10 ̄⁷   wb/A-m       and ε₀  = 8.85 × 10 ̄¹² C²/N-m².


                        C= 1/ √ 4π × 10 ̄⁷ × 8.85 × 10 ̄¹²


                                  C = 3× 10⁷ m/s 

Maxwell concluded that the electromagnetic waves are transverse in nature.

In 1885 , Hertz confirmed experimentally, the existence of electromagnetic waves. In 1895 , an Indian origin physicist J . C . Bose was able to produce electro magnetic waves in the lab and in 1899Marconi  was able to transmit electromagnetic waves up-to few kilometers in space. 


Production of Electromagnetic waves 


The charge at rest produces electric field only. The charge in motion produces electric field as well as magnetic field. If the charges are moving with constant velocity ,then the electromagnetic waves are not produced. If the charge is moving with changing velocity, then electro magnetic waves are produced. In other words, accelerated charge produces electromagnetic waves.


A simple L-C oscillator and an energy source can produce electromagnetic waves of desired frequency.


In practice, these electromagnetic waves are damped. The undamped electromagnetic waves can be produced by pumping some energy known as the feed back energy into the oscillator.


The electromagnetic energy is also produced when an electron from higher energy state jumps to the lower energy state. Ultra violet rays, X-rays, infra red rays are some of the examples of electromagnetic waves.

Important Properties or the facts of Electromagnetic waves :


1) Electromagnetic waves are produced by accelerated charge.


2) Electromagnetic waves do not require any material medium for their propagation. They are free to travel through any kind of medium.


3) The velocity of electromagnetic waves is simply given by the relation; 

                                  C=1/√μ₀ε₀

From this relation it has been founded that the value of velocity of electromagnetic waves is to be  3×10⁷m/s


4) The electric field vector and the magnetic field vector vary simultaneously.


5) The electric field vector and the magnetic field vector are perpendicular to each other and the electromagnetic waves are perpendicular to both E and B.


6) The electromagnetic waves are not deflected by the electric field and the magnetic field.


7) The velocity of electro magnetic waves depends entirely on the electric and the magnetic properties. 


8) The energy of electromagnetic waves is divided equally between electric field vector and the magnetic field vector.


Examples of some of the electromagnetic waves :

X-rays:


The X-rays were first discovered by the professor Roentgen. X-rays can be produced by bombarding a target of high atomic number with a beam of fast moving electrons. 



Visible light :


It is the most familiar form of electromagnetic spectrum . It is the only part of spectrum which is detected by the human eye. Visible light produced in the spectrum which is reflected by the objects provide us information about the world. 

Infra red rays :


Infra red rays are those types of electromagnetic waves which are obtained from hot sources . Therefore, we can say that all the hot bodies are the sources of Infra Red rays. Infra Red rays were first discovered by Hershel , a well known physicist. The range of wavelengths of Infra Red rays is from 7 × 10 ̄⁷  m  to  7 ×  10 ̄⁵  m.


Conclusion:

The article discussed above provides you information related to Electromagnetic waves . The article also explains it's production and the important properties of Electromagnetic waves




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