Convolution for optical broad-beam responses in scattering media
Photon transport theories in Physics, Medicine, and Statistics (such as the Monte Carlo method), are commonly used to model light propagation in tissue. The responses to a pencil beam incident on a scattering medium are referred to as Green's functions or impulse responses.
Source: Wikipedia — Convolution for optical broad-beam responses in scattering media (CC BY-SA 4.0)