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Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectromagnetic Waves

In a plane electromagnetic wave, which of the following quantities possess a zero average value?

Options

  1. AElectric field
  2. BMagnetic energy
  3. CElectric energy
  4. DMagnetic field

Correct answer

D. Magnetic field

Step-by-step solution

In a plane electromagnetic wave, the electric field and magnetic field vary sinusoidally with time and space. The equations for the fields are given by: E = E₀ ( t - kx) B = B₀ ( t - kx) The average value of a sinusoidal function over a complete cycle is zero. Therefore, the average values of the electric field and magnetic field are zero. The electric energy density is u_E = 1 2 ₀ E^2 and the magnetic energy density is u_B = B^2 2 ₀ . Since they depend on the square of the fields, their average values over a compl

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