# centroid wavelength

[4.7.2] λc

The wavelength at the weighted center of the spectrum of a monochromatic device under test (DUT); this is the weighted average of each wavelength and is defined by:

$\lambda _{c}= \left [ \int_{\lambda _1}^{\lambda _2}\lambda \cdot S\left ( \lambda \right)d\lambda \right ]/\left [ \int_{\lambda _1}^{\lambda _2} S\left ( \lambda \right )d\lambda \right ],$

where λ is the wavelength and S(λ) is the spectral power distribution of the monochromatic DUT.