# E=hc/lambda... C

by sorax123
Tags: ehc or lambda
 P: 31 I was thinking about refraction and phase velocity change, when i thought about whether the c in e=hc/lambda is always 3x10^8 or does it refer to the speed in the medium? Thanks
 Homework Sci Advisor HW Helper Thanks PF Gold P: 10,193 in ##E=hc/\lambda## ##c## is always the speed of light in vacuum. if the speed in the medium is important, it will show up in equations as a refractive index. as far as the photon is concerned, the "medium" is an array of atoms with empty space in between.
 P: 31 So if wavelength decreases in a refractive medium, does that mean energy increases???
Homework
HW Helper
Thanks
PF Gold
P: 10,193

## E=hc/lambda... C

No. The relationship in question is the QM one for individual photons.

The EM wave description carries energy differently.
http://farside.ph.utexas.edu/teachin...s/node119.html
... it's a different model.
P: 1,757
 Quote by sorax123 I was thinking about refraction and phase velocity change, when i thought about whether the c in e=hc/lambda is always 3x10^8 or does it refer to the speed in the medium? Thanks
It depends on what do you mean by λ. It is the wavelength in vacuum or in the medium?
Anyway, you should have the formula getting back to E=hf which is valid in vacuum and media as well.
 P: 31 Cheers folks. I now see that the qm and wave models must be evaluated differently and that E=hf is a more useful formula to employ :).

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