# Optical Phenomena#

## Rayleigh Scattering#

colour

 rayleigh_scattering(wavelength[, ...]) Return the Rayleigh optical depth $$T_r(\lambda)$$ as function of wavelength $$\lambda$$ in centimeters (cm). sd_rayleigh_scattering([shape, ...]) Return the Rayleigh spectral distribution for given spectral shape. scattering_cross_section(wavelength[, ...]) Return the scattering cross section per molecule $$\sigma$$ of dry air as function of wavelength $$\lambda$$ in centimeters (cm) using given $$CO_2$$ concentration in parts per million (ppm) and temperature $$T[K]$$ in kelvin degrees following Van de Hulst (1957) method.

colour.phenomena

 rayleigh_optical_depth(wavelength[, ...]) Return the Rayleigh optical depth $$T_r(\lambda)$$ as function of wavelength $$\lambda$$ in centimeters (cm).