Electromagnetic Waves And Their Characteristics

Electromagnetic waves are the type of apparent light that empower us to see our general surroundings. There are various types of electromagnetic waves. Some of them are infrared rays, microwaves, gamma rays, ultraviolet rays, etc. Every wave has a distinctive characteristic – frequency and wavelength range. Hence, they are used in different fields. 

Maxwell was the first researcher who discovered the presence of electromagnetic waves. These waves were produced and detected by Hertz. Later, scientist JC Bose produced an electromagnetic range of wavelength going from 5 mm to 25 mm. Successful transmission of electromagnetic waves up to a few kilometres was done by Macaroni. 

Em Waves And Their Source Of Production-

An electromagnetic wave is a unique wave with three components – the magnetic field (B), the electric field (E), and the direction of wave motion (x). 

Accelerated and oscillating charges produce electromagnetic waves. The waves are created due to vibrations between an electric field and a magnetic field. These waves consist of electric field component E and magnetic field component B. Both E and B are perpendicular to one another. The stage distinction between the two fields is zero.  

The direction of propagation of electromagnetic waves can be represented as-

EB (Cross Product of electric field and magnetic field). 

The amplitude of electric field and magnetic field are related to each other as-

B0= cE0 

Where Eo and Bo are maximum values of electric and magnetic field vectors and c is the speed of light

Characteristics-

Some of the prominent characteristics of electromagnetic waves are-

• These waves do not require any material or medium for propagation.

•  The speed of the electromagnetic wave in a medium is specified by the electric and magnetic properties of the medium and not by the sufficiency of the electric and magnetic field vector. The speed of an electromagnetic wave in a medium can be calculated by-

c = 1/√μoεo

μo is permittivity of free space,

∴ c = Eo/B0

• In free space, these waves travel at speed equal to light. (speed of light c = 3×108 m/s)

• The energy conveyed by electromagnetic waves is similarly split between electric field and magnetic field, and the absolute standard energy bandwidth can be determined as-

UE = (½) εoE² = (¼) εoE²o 

• The electric field vector of an electromagnetic wave produces an optical effect and hence is known as the light factor.
  
  • Electromagnetic waves convey energy just as the force

p = U/c  ,  

p =  momentum

U =   energy carried by an electromagnetic wave in free space

c =  speed of an electromagnetic wave in free space

Types Of Em Waves- 

Precise classification of electromagnetic radiations, as indicated by their recurrence or wavelength, is called electromagnetic range. There is no absolute division between one wave and the other, and the grouping has been done exclusively on how these waves are created or distinguished.

•  Radio waves-

• Produced by accelerating motion of charges in conducting wires
• Frequency range is 500 kHz to 1000 MHz
• Wavelength range is  10-2m to 104m
• Are reflected refracted and diffracted
• These waves have various functions-

• • Used in sky wave communication
  • Used in televisions
  • Used for FM communication
  • Used in cellular phone communication
  • Used in ground wave propagation
    
    

•  Microwaves-

• Produced by special vacuum tubes like magnetrons, Gunn diodes etc.
• Frequency range is 1 GHz to 300GHz
• It is used in-
  • Radar system for aircraft navigation
  • Detect speed of tennis ball, Cricket ball, automobiles
  • Microwave ovens

•  Infrared waves- 

• Produced by a hot body that is due to vibrations of atoms and molecules
• Cannot be detected by the human eye
• They are readily absorbed by water, carbon dioxide, ammonia, etc. 
• Frequency range is 10 11 Hz to 1014 Hz
• Wavelength range is 1m to 700mm
• Detected by thermophiles, infrared photographic film
• The use of these waves are-

• •  Infrared lamp used in physical therapy or to treat muscular strain
  •  Provide electrical energy to a satellite by using solar cells
  •  Take photographs during fog and smoke
  •  To study molecular structure by taking infrared absorption spectrum
    
    

•  Visible light- 

• Produced by atomic excitation
• Frequency range is 4*1014 Hz to 7*1014 Hz
• Wavelength range is 700 nm is 400nm
• It can be detected by eyes, photocells, photographic films
  
  

•  Ultraviolet rays- 

• Produced by the sun, special lamps, and very hot bodies
• Frequency range is 8 ✕1014 Hz to 5*10 16 Hz
• Wavelength range is 400nm to 0.6nm
• If produced in large quantity then it can be harmful to humans

•  X-rays-

• Produced in a tube called modern x-ray tube
• Frequency range is 1016 Hz to 1021 Hz
• Wavelength range is 10 nm to 10 -4 nm
• Detected by photographic film, Geiger tubes and ionisation chamber
• It is used in- 

• Detecting   faults,  cracks,  flaws and holds in engineering
• Detecting pearls in oysters,  defect in rubber tyres and gold

•  Gamma rays- 

• They are produced in nuclear reactions and are emitted by radioactive nuclei
• The frequency range is 10 18 Hz to 1022 Hz
• Wavelength is <10-3nm
• They show phosphorescence,  fluorescence,  polarisation and diffraction
• They have very high penetrating power
• They are used in cancer therapy
• They provide information about nuclear structure

Conclusion

The fundamental difference between various electromagnetic waves lies in their wavelengths and frequencies since they all travel through a vacuum with the same speed. The waves also differ considerably in their mode of interaction with the matter. Hence, according to the wavelength and frequencies, the different electromagnetic waves are organised with the electromagnetic spectrum.