# E=hc/lambda C

1. Feb 5, 2013

### 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

2. Feb 5, 2013

### Simon Bridge

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.

3. Feb 6, 2013

### sorax123

So if wavelength decreases in a refractive medium, does that mean energy increases???

4. Feb 6, 2013

5. Feb 6, 2013

### nasu

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.

6. Feb 6, 2013

### sorax123

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 :).