The electric field in an electro-magnetic wave (in vacuum) is described by E = Emax sin(Kx - ωt)

Where

Emax = 100 N/C and K = 1 × 107 m-1, speed of light is 3 × 108 m/s.

What is the amplitude of the corresponding magnetic wave?

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ESE Electronics 2014 Paper 1: Official Paper
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  1. 4.57 × 10-7 T
  2. 2.99 × 10-7 T
  3. 3.33 × 10-7 T
  4. 2.99 × 107 T

Answer (Detailed Solution Below)

Option 3 : 3.33 × 10-7 T
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Detailed Solution

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Concept:

The intrinsic impedance of the wave is defined as the ratio of the electric field and the magnetic field phasor (complex amplitude), i.e.

For free-space, the intrinsic impedance is a real quantity, i.e.

η  = η0 = 120π

Analysis:

E = Emax sin(Kx - ωt)

With Emax = 100 N/C, the magnetic field will be:

With :

B = μ0 H

B = 3.33 × 10-7 T

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