Question

State the important characteristics of electromagnetic waves.

Hint:

Recall that EM waves are transverse (\(\vec E\perp\vec B\perp\) propagation), travel at \(c=1/\sqrt{\mu_0\varepsilon_0}\) with \(E_0=cB_0\), need no medium and carry energy and momentum.

Answer 1

Important characteristics of electromagnetic waves:
1. They are produced by accelerating (oscillating) charges and consist of an oscillating electric field \(\vec{E}\) and magnetic field \(\vec{B}\).
2. They are transverse: \(\vec{E}\) and \(\vec{B}\) are perpendicular to each other and both are perpendicular to the direction of propagation.
3. \(\vec{E}\) and \(\vec{B}\) oscillate in the same phase, and their amplitudes are related by \(E_0 = cB_0\).
4. They do not need any material medium and can travel through vacuum.
5. In vacuum they all travel with the same speed \(c = \dfrac{1}{\sqrt{\mu_0\varepsilon_0}} = 3\times10^{8}\ \text{m/s}\).
6. They carry energy and momentum and exert radiation pressure; the energy is shared equally between the electric and magnetic fields.
7. Being uncharged, they are not deflected by electric or magnetic fields.
8. They show reflection, refraction, interference, diffraction and polarization, and obey the superposition principle.
\[\boxed{\text{Transverse, need no medium, speed }c,\quad E_0=cB_0}\]