2020 Electromagnetic WavesElectromagnetic Waves – Energy Density Medium Question 20 of 49 in Electromagnetic Waves

The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: ($c$ = speed of electromagnetic waves)

A $1:1$
B $1:c$
C $1:c^2$
D $c:1$

The answer is A.

Solution

In an electromagnetic wave, the energy densities of the electric and magnetic fields are equal: $\frac{1}{2}\epsilon_0E^2 = \frac{B^2}{2\mu_0}$ So half of the intensity is provided by the electric field and half by the magnetic field. Required ratio = 1 : 1

Concept equal contribution of E and B to intensity

Electromagnetic Waves in past papers

49 questions from this chapter have appeared across 24 exam years.