# Need Help Remembering An Equation

Hertz
Does anyone happen to know the equation to convert frequency into energy?
I think it's something like: E = hf, but I'm not sure.

Any help is appreciated :)

whybother
E = hf

Yup. I assume you mean for EM waves?

Hertz
Yup, is that the right equation?

whybother
Yes.

Hertz
So this means that mc^2 = hf right?
So does this mean that everything with mass is actually an EM wave? Sorry I don't know a whole lot, I'm still in 11th grade :\

whybother
No, that's not what it means, that's why I asked if you meant for EM waves.
While yes, all matter does have an associated wavelength, but no, you can't compare the rest mass energy to the energy for an EM wave.

For photons, $$E=h f$$ where the momentum of a photon is given by,
$$p = {E \over c}$$
$$\lambda = {h \over p}$$
Where $$\lambda$$ is the associated wavelength.
In general, energy is not just the rest mass energy and also includes a momentum term, so for our massive particles we have: $$E^2 = m^2 c^4 + p^2 c^2$$