# Unit conversion

1. Feb 25, 2009

### Rajini

Dear PF members,
We know that 1 meV = 8.066 cm-1. So now can i say 1 cm = 8.066 meV-1 ????
Ps: 1 cm-1 = 0.124 meV.

2. Feb 25, 2009

I'm not sure what you are saying here Rajini because your units dont balance.An eV is a unit of energy.

3. Feb 25, 2009

### ZapperZ

Staff Emeritus
This is a common "short form" used in condensed matter/solid state physics, especially in optical conductivity measurement. 1 eV is "equivalent" to 8.0655 x 10^3 cm^-1. It's one of those simplified notation that sets k=h=c=1.

Zz.

4. Feb 25, 2009

5. Feb 25, 2009

### ZapperZ

Staff Emeritus
It actually is a straight-forward conversion.

So if you have 1 eV = hf, it gives you an equivalence

1 eV == 2.4 e14 Hz

but we know that f = c/lambda.

So 1/lambda = cf = 8.05 e3/cm == 1 eV.

The list of values of the conversion from 1 eV into frequency, 1/cm, and Kelvin can be found in the inside back cover of Ashcroft and Mermin's Solid State Text.

Zz.

6. Feb 25, 2009

### Rajini

Hi, how i calculate (and many ppl. do)..
we know
$$E=hc/\lambda$$
and so
$$1/\lambda=E/(hc)$$
Now by taking E = 1 eV, h in eVs and c in cm/s
one will get $$1/\lambda$$ = 8066 cm-1 (for E= 1 eV).
So 1 meV = 8.066 cm-1
But my questions is whether the following is correct or not!!!!!???
1 cm = 8.066 meV-1 [i just reversed the units!]

7. Feb 25, 2009

### Rajini

yes i solved this problem..sorry

8. Feb 25, 2009