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JEE MainPhysicsElectromagnetic Waves

An electromagnetic wave is traveling through a non-magnetic dielectric medium of relative permittivity _r . If the amplitude of the electric field in the medium is E₀ and the speed of light in vacuum is c , the amplitude of the magnetic field B₀ in the medium is:

Options

  1. AB₀ = E₀ c _r
  2. BB₀ = E₀ c _r
  3. CB₀ = E₀ _r c
  4. DB₀ = E₀ _r c

Correct answer

C. B₀ = E₀ _r c

Step-by-step solution

The speed of an electromagnetic wave in a medium is given by: v = c _r _r For a non-magnetic medium, the relative permeability _r = 1 . Therefore, the speed of the wave in the dielectric medium is: v = c _r The ratio of the electric field amplitude to the magnetic field amplitude in any medium is equal to the speed of the wave in that medium: E₀ B₀ = v Substituting the expression for v , we get: E₀ B₀ = c _r Rearranging to solve for B₀ , we obtain: B₀ = E₀ _r c Answer: B₀ = E₀ _r c

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