Problem — Ratio of E0 to B0

Problem

A plane EM wave propagates in vacuum with electric field amplitude $E_0=600$ V/m. Calculate the amplitude $B_0$ of the magnetic field.

Solution

Fundamental relation. In a plane EM wave in vacuum the magnitudes are related by $E=cB$, so for the amplitudes:

$B_0=\frac{E_0}{c}=\frac{600}{3{,}00\cdot 10^8}=2{,}0\cdot 10^{-6}\ \text{T}$

$\ev{B_0=2{,}0\cdot 10^{-6}\ \text{T}=2{,}0\ \mu\text{T}}$

The magnetic field is numerically tiny because it is divided by $c$: consistent with the fact that the energy is equally shared between the two fields.

Collegamenti

Argomenti: Onde elettromagnetiche Concetti: Onda elettromagnetica · Campo magnetico