There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. (arxiv.org)
Our results suggest that a short path length is crucial for efficient information processing across the functional brain network and leading toward a high IQ. (jneurosci.org)
Just to give an example, the mean free path length of photons in the CO2 at its current density in the atmosphere is 48 meters. (wattsupwiththat.com)