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I saw a proof in a book for the de broglie equation which I thought was wrong.
if l = lambda, so wavelength and then all other notation is standard they said:
E=mc^2
E=hf
therefore,
mc^2=hf
but for a photon, c=v
so:
mv^2=hf
but mv=P
so:
Pv=hf
and v=fl
so:
Pfl=hf
Pl=h
and finally:
l=h/P
Anyway, that's what they said. But I thought since a photon doesn't have a mass "mv" couldn't be its momentum. Or does it not matter?
if l = lambda, so wavelength and then all other notation is standard they said:
E=mc^2
E=hf
therefore,
mc^2=hf
but for a photon, c=v
so:
mv^2=hf
but mv=P
so:
Pv=hf
and v=fl
so:
Pfl=hf
Pl=h
and finally:
l=h/P
Anyway, that's what they said. But I thought since a photon doesn't have a mass "mv" couldn't be its momentum. Or does it not matter?