With regard to the wave/particle duality of light, does Big Bang red shift affect both the frequency of light waves, and, the frequency of individual photons? I assume that the e=hf formula relates to individual photons, and not to light waves too?

  • $\begingroup$ Individual photons are light waves though. That's the point behind particle-wave duality. Light is both a particle and a wave. That means, for a given light quanta, when we talk about it redshifting, we're referencing the wave form of the quanta. $\endgroup$ – zephyr Aug 1 '16 at 15:45
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    $\begingroup$ The "duality" is just an explanation gimmick. Photons are not inherently "dual" in any real sense. They are neither corpuscles in the classic sense, but neither are they just waves. Photons are quantum objects with clearly defined properties, just like any other quantum objects. It just so happens that some of those properties are corpuscle-like, while other properties are wave-like. It's like saying an airplane has a bird-truck duality: bird because it has wings, and truck because it has an engine. But in reality planes are neither birds nor trucks, but something entirely different from both. $\endgroup$ – Florin Andrei Aug 1 '16 at 20:32

Yes it affects both. If you treat light as waves then the wavelength from a source at a redshift $z$ is "stretched" by a factor of $1+z$.

Photons emitted from a source at redshift $z$ have their energies reduced by a factor of $1+z$.


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