Is 1 cm equal to 8.066 meV-1 in unit conversion?

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Discussion Overview

The discussion revolves around the unit conversion between centimeters and meV, specifically whether 1 cm can be accurately expressed as 8.066 meV-1. The scope includes theoretical considerations and unit conversions relevant to physics, particularly in the context of energy and wavelength.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant states that 1 meV equals 8.066 cm-1 and questions if this implies that 1 cm equals 8.066 meV-1.
  • Another participant expresses confusion, noting that the units do not balance, as eV is a unit of energy.
  • A different participant mentions that the conversion is commonly used in condensed matter physics, particularly in optical conductivity measurements, and provides a numerical equivalence of 1 eV to 8.0655 x 103 cm-1.
  • One participant provides a derivation starting from the equation E=hf, explaining how the conversion can be understood in terms of frequency and wavelength.
  • Another participant confirms the conversion and emphasizes the importance of distinguishing between meV-1 and milli-eV-1, sharing a personal anecdote about initial confusion with cm-1.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the unit conversion, with some supporting the conversion and others questioning the balance of units. The discussion remains unresolved regarding the validity of stating 1 cm as 8.066 meV-1.

Contextual Notes

There are limitations in the discussion regarding the assumptions made in unit conversions and the potential for confusion between similar notations. The derivations presented depend on specific definitions and contexts within physics.

Rajini
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Dear PF members,
We know that 1 meV = 8.066 cm-1. So now can i say 1 cm = 8.066 meV-1 ?
thanks for your reply.
Ps: 1 cm-1 = 0.124 meV.
 
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I'm not sure what you are saying here Rajini because your units don't balance.An eV is a unit of energy.
 
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.
 
Whoops...sorry Rajini and thank you ZapperZ.Can you please give me some ideas about where to google to get more information?
 
Dadface said:
Whoops...sorry Rajini and thank you ZapperZ.Can you please give me some ideas about where to google to get more information?

It actually is a straight-forward conversion.

Start with E=hf.

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.
 
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!]

thanks for your reply
 
yes i solved this problem..sorry
 
THank you ZapperZ.There was I thinking it might be something complicated.
 
Rajini said:
But my questions is whether the following is correct or not!?
1 cm = 8.066 meV-1 [i just reversed the units!]

Yes, but remember here that it's (meV)-1 and not milli-(eV)-1,
just as cm-1 is taken to mean 1/centimeters and not 100ths of 1/m.

First time I worked with cm-1 I kept being off by a factor of 10,000 for some reason :)
 

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