If waves are defined as the oscillation of a medium, why are electromagnetic waves called waves as they do not need a medium to travel through?
[Physics] Why are electromagnetic waves called waves even though they don’t travel through a medium
electromagnetic-radiationterminologywaves
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Best Answer
The definition of a wave is not that it is the oscillation of a medium. Waves are called waves because they are solutions to a wave equation, which is, for a generic "excitation" $A(t,x)$ depending on the time $t$ and some spatial coordinate $x\in\mathbb{R}^n$, of the general form
$$ \frac{\partial^2 A}{\partial t^2} = c^2\Delta A$$
where $\Delta$ is the Laplacian for the spatial coordinate. The wave equation, in turn, is called a wave equation because it is precisely the equation that governs the archetypical system where a wave occurs - that of masses linearly connected by springs.
While a wave equation may arise from considering a medium, a medium is not necessary for a wave equation to occur, as Maxwell's equations and the disproof of almost all luminiferous aether theories show.