Which statement correctly describes the propagation of electromagnetic waves in vacuum?

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Multiple Choice

Which statement correctly describes the propagation of electromagnetic waves in vacuum?

All electromagnetic waves travel through vacuum at the same speed—the speed of light, c. This happens because there’s no medium to slow different wavelengths differently, so the vacuum’s refractive index is effectively 1 for all frequencies. The relation v = fλ ties frequency and wavelength to this constant speed, so as frequency changes, wavelength adjusts (λ = c/f) but the speed remains c for every wave, from radio to gamma rays. The other statements would imply dispersion in vacuum, require a medium, or claim only some waves propagate, none of which is true.

All electromagnetic waves travel through vacuum at the same speed—the speed of light, c. This happens because there’s no medium to slow different wavelengths differently, so the vacuum’s refractive index is effectively 1 for all frequencies. The relation v = fλ ties frequency and wavelength to this constant speed, so as frequency changes, wavelength adjusts (λ = c/f) but the speed remains c for every wave, from radio to gamma rays. The other statements would imply dispersion in vacuum, require a medium, or claim only some waves propagate, none of which is true.

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