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12th physics online class and notes -Electromagnetic Waves

12th physics online class and notes -Electromagnetic Waves

Physics notes for class 12 : How are Electromagnetic waves produced?
Electromagnetic waves are produced by an accelerated or de-accelerated charge or LC circuit.
Transverse Nature of Electromagnetic waves:The Electromagnetic waves are transverse in nature with the electric and magnetic fields perpendicular to the direction of propagation.

Electromagnetic waves: The waves propagating in space through electric and magnetic fields varying in space and time simultaneously are called electromagnetic waves.
  • An electromagnetic wave consists of a fluctuating electric field and a fluctuating magnetic field of the same frequency and the same phase.
  • The electric and magnetic fields are mutually perpendicular and also perpendicular to the direction of propagation of the wave.
  • In the propagation of an electromagnetic wave, a varying electric field E gives rise to a varying magnetic field and so on. In this way, electric and magnetic fields of the wave sustain each other.

Characteristics of electromagnetic waves:
  • The electromagnetic waves travel in free space with speed of light irrespective of their wave length.
  • Electromagnetic waves are transverse in nature.
  • Electromagnetic waves do not need a material medium for their
propagation.
  • Electromagnetic waves are produced by accelerated charges.
  • Electromagnetic waves obey the principle of superposition.

  • Electromagnetic waves are neutral so they are not deflected by electric and magnetic fields.
  • The ratio of magnitudes of electric and magnetic field vectors in free space is constant and equal to c
ie c = E/B = 3×108m/s

  • Electromagnetic waves show properties of reflection, refraction, interference,
diffraction and polarisation.
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