Physical significance of wavenumber

[pallavi12]

i do not understand what is the physical significance of wavenumber.
i have a plot with wavenumber on x-axis and count on the y axis.
what does the plot mean, how can i relate to a practical example. please help

 

[Petr Mugver]

Wavenumber is related to wavelength by

$$k=\frac{2\pi}{\lambda}$$

Maybe you are counting the number of photons of a certain wavelength that reach a detector?