How is shadow created

Shadow formation

Shadows arise where the light is prevented from spreading in a straight line by opaque objects. A shadow is thus created on the side of an opaque body facing away from the light source.

Per light source arises a shadow on an opaque object. It doesn't matter whether it is a real or a virtual light source.

The closer a light source is to the object, the larger the shadow it creates.

If two shadows overlap, a darker one is created Umbra. These areas appear dark because no light can get there. No light source illuminates this section. The lighter shadow sections (see picture above) are called Penumbra or drop shadow. These areas appear brighter because the light from one light source reaches here, but that of another does not.

With the help of geometrical optics and the light beam model, predictions can be made by drawing how a light source casts a shadow on an object. For this purpose, it is advantageous to look at what is happening from a bird's eye view.

To construct a shadow, draw in the two rays of light that just make it past the obstacle. All rays of light between these two hit the obstacle (also Shadow giver called) and cannot spread any further. All light rays outside of these two make it past the obstacle. This creates the shadow between these light rays on the side facing away from the light source (see picture below).

If several light sources are available, this construction is carried out for all light sources available in order to obtain the shadow image. If the light paths overlap behind the object, it must be ensured that core and penumbra are created (see picture below).

If the light paths do not overlap, only penumbra appears, but no umbra.