Question

what is this ray shadow called

Answer 1

A point source of light casts only a simple shadow, called an "umbra". For a non-point or "extended" source of light, the shadow is divided into the umbra, penumbra and antumbra. ... This is known as the Shadow blister effect.

Answer 2

Answer:

Shadow ray is the last segment on the light path traveling through the scene (from camera to light source). ... When the light path begins, it starts as a camera ray, when its reflected it becomes reflection ray, when it goes through glass it becomes transmission ray and from the last point to lamp it is shadow ray.