Question

(a) On what factors does the speed of an electromagnetic wave in a medium depend?
(b) How is an electromagnetic wave produced?
(c) Sketch a schematic diagram depicting the electric and magnetic fields for an electromagnetic wave propagating along the z-axis.

Hint:

The speed of electromagnetic waves in a medium depends on the permittivity and permeability of the medium.

Answer 1

(a) The speed \( v \) of an electromagnetic wave in a medium depends on: The permittivity \( \epsilon \) of the medium. The magnetic permeability \( \mu \) of the medium. The speed of EM waves is given by: \[ v = \frac{1}{\sqrt{\mu \epsilon}}. \] (b) Electromagnetic waves are produced by oscillating or accelerated charges, such as electrons in an antenna. These oscillating charges generate both electric and magnetic fields that propagate through space as an electromagnetic wave. (c) The electric and magnetic fields for an electromagnetic wave propagating along the z-axis are perpendicular to each other and the direction of propagation. The electric field oscillates along the x-axis and the magnetic field along the y-axis, as shown in the diagram:
\includegraphics[width=0.5\linewidth]{ph23.c.png}
\[ \text{Electric Field (E)} \quad \text{and} \quad \text{Magnetic Field (B)} \quad \text{in the direction of propagation (z-axis)}. \]