I was reading the derivation of this equation on hyperphysics.com and after searching all over the internet it seems that eveywhere seems to just accept this equation is valid for light, even though a rest mass of 0 would make p equal to 0.(adsbygoogle = window.adsbygoogle || []).push({});

Sorry if I'm being stupid or if this has been asked a million times before but I can't find an explanation anywhere as to why light having zero rest mass gives the equation E = pc, despite p being proportional to the (zero) rest mass of light.

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# E = pc derivation

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