# Question 72152

Mar 25, 2017

Electromagnetic waves are non elastic waves in the sense that they don't really need a material medium for their propagation like sound waves do.

EM waves, as I shall call them are basically perpendicularly oscillating electric and magnetic fields propagating in space. The Oscillating fields oscillate transversely i.e. perpendicular to the direction of propagation.

Their velocity in a particular medium is determined thus by the electrical and magnetic properties of the medium.
In vacuum, they propagate with a velocity approximately given as
$c = 3 \cdot {10}^{8} m {s}^{- 1}$

In presence of material medium their velocity is smaller than this and is given as

$v = {\left(\epsilon \cdot \mu\right)}^{- \frac{1}{2}}$
where
ε is the electrical permittivity and
μ# is the magnetic permeability.