Practice portal › Electromagnetic Waves › Speed of EM Waves and Media
Asked in RS Academy GUJCET booklet · Speed in vacuum and in a medium
Idea: Maxwell's equations fix the speed of an electromagnetic wave in vacuum from two constants of the vacuum alone, c=1/(√μ₀ε₀).
Neither μ₀ nor ε₀ depends on the frequency of the wave, so every electromagnetic wave travels at the same 3×10⁸ m s⁻¹ in space.
γ-rays, X-rays and microwaves differ enormously in wavelength and in photon energy, but not at all in speed.
So v_γ = vₓ = vₘ.
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