UHP beam in the rain 2

Here's a closer look at the light beam passing through heavy rain (see general view there), viewed from the side with light going from left to right. The dark zone corresponding to the total internal reflection of light in the water droplets can be clearly seen on the left. This zone is bordered by messy rainbows which arise from the wavelength-dependent refraction of light in water. This colored effect is not as clean as in proper rainbows because of a great variability in the shape and size of the water drops and the very short viewing distance. Note also that there is a clear optimum in the sideways light reflection, where all colors are refracted in and exit the droplets. Beyond that point, on the right, what we see is more the result of light scattering from air-water surface (Fresnel) reflections than light refraction in the droplets. Distance plays also a role in the diminishing brightness of the beam as seen from the present vantage point (i.e, that's the inverse square law at work there). Interestingly, there is a secondary (mildly) dark zone on the right, caused by the transition from an internal refraction-dominated to an external reflection-dominated process, and the fact that the magnitude of the Fresnel reflection is angle-dependant. There's a lot going on in pouring rain crossed by a light beam indeed.