The fomula h/lambda is this for the photon only?

1. Feb 25, 2006

UrbanXrisis

the fomula $$\frac{h}{\lambda}$$

is this for the photon only? or can it be applied to relativistic electrons too?

2. Feb 25, 2006

anjor

it applies to particles with zero rest mass. Hence it wont apply to relativistic electrons.

3. Feb 26, 2006

UrbanXrisis

so for relativistic electrons, if I wanted it's speed, i'd use .5mv^2?

4. Feb 26, 2006

dicerandom

1/2 m v^2 only works for non-relatavistic speeds, the energy for a relatavistic particle is different. See here for more details.

5. Feb 26, 2006

gulsen

Same question was asked by de Brolie. And actually, it turned out that it will.

6. Feb 26, 2006

topsquark

Yes, but UrbanXrises' original formula was either a typo or assumed that c=1. With c=1 this formula is, in fact, only good for massless particles. DeBroglie's relationship involves the speed, which is less than c.

-Dan

7. Feb 26, 2006

gulsen

No, it comes from:
$$E = pc = \frac{hc}{\lambda}$$
where c's cancel, and de Broglie's equation relates momentum and wavelength.

8. Feb 26, 2006

topsquark

I was thinking of the energy equation. Sorry! (Ahem!)

Even though I got my c's wrong, the argument still holds...E=pc only hold for massless particles, which was what I was trying to say.

-Dan

Last edited: Feb 26, 2006
9. Feb 26, 2006

UrbanXrisis

so $$p=\frac{h}{\lambda}$$ is for massless particles

but what about $$E=fh$$?

is this equation for massless particles too?

10. Feb 26, 2006

topsquark

No. This equation is good for anything. Basically this equation simply expresses the quantizability of energy.

-Dan

11. Feb 27, 2006

gulsen

No, it applies to all particles! That's the backbone for Schrödinger equation!