- #1

TheCelt

- 24

- 5

- Homework Statement
- Units for photon momentum confuse me

- Relevant Equations
- p=hf/c = E/c

So if i have a photon of some energy and i want to find the magnitude of the momentum, i can get the right answer but the units don't make sense.

So i derive p = E/c since i know the energy of the photon and i used f=E/h and substituted this into p=hf/c

This means for units of the equation p = E/c i get:

kg m/s = J / (m/s) = J s/m

This is confusing me since I've always been told to check my units but these equations don't have the same units, so I don't know if i have done something wrong, or momentum has different units applied for photons? Hope some one can explain what's going on here with the units.

Thanks

So i derive p = E/c since i know the energy of the photon and i used f=E/h and substituted this into p=hf/c

This means for units of the equation p = E/c i get:

kg m/s = J / (m/s) = J s/m

This is confusing me since I've always been told to check my units but these equations don't have the same units, so I don't know if i have done something wrong, or momentum has different units applied for photons? Hope some one can explain what's going on here with the units.

Thanks