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Electromagnetic Waves — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves3 Marks
Question
  1. How are electromagnetic waves produced? Explain.
  2. A plane electromagnetic wave is travelling through a medium along the +ve z-direction. Depict the electromagnetic wave showing the directions of the oscillating electric and magnetic fields.
✓

Answer

  1. Electromagnetic waves are formed as a result of accelerating (electric) charges under electric field. Electric charge exhibit electrostatic behaviour and once they start moving magnetic effects come into play. As a result of this a duality is established which is called electromagnetism. The electromagnetic waves are emitted by those charged particles. These waves move with the velocity of light
  2. The cross product of electric and magnetic field vectors i.e.$\vec{E}\times\vec{B}$  gives the direction in which the wave travels.

It is given that wave is propagating along the +z-axis. This means that electric field vector is oscillating in positive x- direction and magnetic field vector in positive y-direction.

The propagation of electromagnetic wave in +z direction is shown here:

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