Halo (natural phenomenon)

A halo around the shadow of his observer

The halo is an optical phenomenon that can be seen as a lightening around the observer's shadow. If the observer moves, the halo moves with it.

Emergence

The halo can be observed early in the morning on deaf meadows. Like lenses, the dew drops focus the sunlight on the plants in the background. The light is backscattered from the plant surface. Since the backscattered light crosses the dewdrop, the brightest area is created around the opposite point of the sun, i.e. the connecting line between sun, observer and shadow.

In order for the light from the drops to be focused, the dewdrop must have a certain distance from the plant. Therefore, the halo can be seen particularly on rough plants, the hairs of which keep the drops from the plant at a distance.