The smallest angle through which light is deviated when undergoing refraction in particles such as water droplets or ice crystals. This angle depends upon the refractive index of the material: for a simple pathway through a raindrop it is c.42°, and for a hexagonal ice crystal c.22°. These correspond to the radii of the primary rainbow and 22° halo, respectively. Rays emerging at the minimum deviation make the greatest contribution to the brightness of the final image.
Subjects: Meteorology and Climatology.