What is the density of spectra?

The density of spectra refers to the distribution of spectral power or intensity across different wavelengths or frequencies in a given signal or electromagnetic spectrum. It quantifies how much energy is present at each frequency, often represented in units like watts per hertz (W/Hz) or similar. This concept is crucial in fields like optics, acoustics, and telecommunications, as it helps in analyzing and interpreting the characteristics of waves and signals.