Hi all,(adsbygoogle = window.adsbygoogle || []).push({});

When thinking about equations of momentum for photons and i came up with this problem.

Say you take the equation E=mc^2 and re-arrange it so m is the subject, m=E/(c^2)

Now the Energy of a photon is also given by the equation Ep=hf and the 'mass' can therefore be said as m=hf/(c^2)

Now momentum is said to = mv so the momentum of the photon should =hf/c.

My question is this, how is it this equation works when it relies on the fact that E=mc^2; as photon has no mass should it not have any energy? (Which it clearly does). I am also confused by the fact that is combines to separate energy equations i.e. Ep=hf which is designed to overcome the problems that occur when calculating the energy of a photon with E=mc^2.

Is this due to the fact that the mass is equivalent to the energy of the photon as in Relativity?

PS: Does this forum support LaTeX, and if so any resources on using it would be much appreciated.

Thank you for any help in advance

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# Photon Momentum

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