Electromagnetic Waves

•    The existence of electromagnetic waves was demonstrated by Hertz. These waves are used for establishing a communication between two locations at a distance of about 50 km, without the use of wires.
•    The concept of displacement current was introduced by Maxwell; he found that Ampere’s circuital law is logically inconsistent.  To make Ampere’s circuital law consistent, Maxwell introduced the concept of displacement current, which is known as Ampere Maxwell’s law.
•    In Electromagnetic waves there are sinusoidal electric and magnetic field vectors varying perpendicular to each other as well as to the direction of propagation of wave.
•    An accelerated charge acts as the source of electromagnetic waves. They do not require a material medium for their propagation.
•    The orderly distribution of electromagnetic radiations according to their wavelength or frequency is known as Electromagnetic Spectrum.


              

•    It has wide range with wavelength variation of 10-14 m to 6 x 102 m. The electromagnetic spectrum has been classified into different parts and subparts in the order of increasing wavelength or frequency.
•    The physical properties of electromagnetic waves are decided according to their wavelengths.
•    Radio waves which are used for different types of wireless communication.
•    Microwaves used in microwave ovens for cooking purpose.
•    Infrared rays or heat waves used in physiotherapy
•    Visible rays which help us to see the colorful world.
•    Ultraviolet rays used to detect fake currency and purify water.
•    X- rays used for the detection of fractures, foreign bodies like bullets, diseased organs and stones in the human body.
•    Gamma rays used in the treatment of cancer and tumors.

 

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