Physics Course/Types of Waves/Electromagnetic Waves

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Electromagnetic Waves

Onde electromagnetique.svg

Electromagnetic Wave is a wave compose of two waves An Electric Wave perpendicular to a Magnetic Wave travels in one direction . ElectroMagnetic Wave is observed in

  1. Electric Radiation or Black Body Radiation
  2. EletroMagnetic Radiation
  3. Nucleus Decays Radiation

Electromagnetic Waves Characteristics

EM waves are typically described by any of the following three physical properties

Frequency , f
Wavelength , λ
Energy photon , E
  • Speed
Electromagnetic Radiation travels at a speed equal to the speed of light in a vacuum C ≈ 3 x 108 m/s .
  • Wavelength
Since all Electromagnetic Radiation travels at a speed of light , If the frequency of Electromagnetic Radiation is known then the wavelength can be calculated
  • Energy

The energy of all Electromagnetic Radiation is quantized calculated by Plank's Formula


c = 299792458 m/s , speed of light in vacuum
h = 6.62606896 Js , Planck's constant

Electromagnetic Radiation Spectrum

EM Spectrum Properties edit.svg

Electromagnetic spectrum of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. The electromagnetic spectrum extends from below frequencies used for modern radio to gamma radiation at the short-wavelength end, covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. The long wavelength limit is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length, although in principle the spectrum is infinite and continuous.

The Frequency Range of Electromagnetic Radiation Spectrum include frequencies of

  1. Radio Waves
  2. Microwave
  3. Infrared Wave
  4. Visible Light
  5. Ultra Violet Waves
  6. X Rays
  7. Gamma Rays


Classifications of Electromagnetic Waves

Light spectrum.svg

Electromagnetic radiation and Matter

Electromagnetic radiation interacts with matter in different ways in different parts of the spectrum. The types of interaction can be so different that it seems to be justified to refer to different types of radiation. At the same time, there is a continuum containing all these "different kinds" of electromagnetic radiation. Thus we refer to a spectrum, but divide it up based on the different interactions with matter.

Region of the spectrum Main interactions with matter
Radio Collective oscillation of charge carriers in bulk material (plasma oscillation). An example would be the oscillation of the electrons in an antenna.
Microwave through far infrared Plasma oscillation, molecular rotation
Near infrared Molecular vibration, plasma oscillation (in metals only)
Visible Molecular electron excitation (including pigment molecules found in the human retina), plasma oscillations (in metals only)
Ultraviolet Excitation of molecular and atomic valence electrons, including ejection of the electrons (photoelectric effect)
X-rays Excitation and ejection of core atomic electrons, Compton scattering (for low atomic numbers)
Gamma rays Energetic ejection of core electrons in heavy elements, Compton scattering (for all atomic numbers), excitation of atomic nuclei, including dissociation of nuclei
High energy gamma rays Creation of particle-antiparticle pairs. At very high energies a single photon can create a shower of high energy particles and antiparticles upon interaction with matter.


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