# Frequence and wavenumbers

#### asdf1

if frequency is (1/sec), then why is wavenumber (1/cm) considered a unit of frequency?

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#### Hootenanny

Staff Emeritus
Gold Member
asdf1 said:
if frequency is (1/sec), then why is wavenumber (1/cm) considered a unit of frequency?
It is considered the spatial representation of frequency, it in itself is not a fequency. However, you can obtain the the wavenumber by dividing the frequency by the speed of light. Observe,

$$c = f\lambda \Leftrightarrow \frac{1}{\lambda} = \frac{f}{c}$$

$$\frac{1}{\lambda}\propto f$$

#### asdf1

wow! never thought of it that way before~ thank you!!!

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