- 33

- 0

Hi all,

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

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

Last edited: