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 (ε) of the medium
• The magnetic permeability (μ) of the medium

The speed of an electromagnetic wave 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 moving charges generate time-varying electric and magnetic fields, which propagate through space as electromagnetic waves.

(c) For an electromagnetic wave travelling along the z-axis, the electric field and magnetic field are:

• Perpendicular to each other
• Perpendicular to the direction of propagation

Specifically, the electric field oscillates along the x-axis, while the magnetic field oscillates along the y-axis. The wave propagates in the z-direction.

\[ \text{Electric Field (E)} \;\perp\; \text{Magnetic Field (B)} \;\perp\; \text{Direction of propagation (z-axis)} \]