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Those of you who have read Bohr's Theory in Chemistry may have encountered the relation,

[tex]

\frac{1}{\lambda} = RhcZ^{2}(\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}})

[/tex]

for the wavelength of radiation emitted when an electron goes from a higher energy level [tex]n_{2}[/tex] to a lower energy level [tex]n_{1}[/tex], R is the Rydberg Constant, c is the speed of light and Z is the atomic number of the one-electron (hydrogen-like) species being considered.

Now some books refer to the fraction [tex]\frac{1}{\lambda}[/tex] as the "wavenumber", whereas in physics, the fraction [tex]\frac{2\pi}{\lambda}[/tex] is called the wavenumber. Why should this difference exist at all?

I was told by my teachers to make a distinction when answering questions on physics (use the second formula) and chemistry (use the first one) but that to me seems hardly convincing.

Cheers

Vivek

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# Difference in Physics and Chemistry Text regarding Wavenumber

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