What Is A Shadow?
A shadow is a real image (dark) expanse where light from a light source is blocked by an opaque (not able to be seen through; not transparent) object. It holds all the 3D volumes behind an object with light in front of it. The cross-section of a shadow is a 2D silhouette (the dark shape and outline of someone or something visible in restricted light against a brighter background) or an opposite projection of the object blocking the light.
How Is Shadow Formed?
We need to understand what is light? Visible light or light is electromagnetic radiation, having both electric and magnetic components that can be perceived by our eyes.
It is a form of energy, so we can recognize any region without these electromagnetic radiations (which are visible to the human eye) as dark.
Do you know the fire has no shadow! If you want to the Reason Why There's No Shadow of Fire?
Opaque Objects
Light is a kind of energy that can be absorbed. If the object can't absorb light, the light can move through these objects, we call these objects transparent. The objects that are optically dense enough, partially absorb and partially let the light move through them are called translucent (semi-transparent), and the objects that are very dense optically, that the light can't penetrate them, and therefore it gets absorbed and reflected, but it cannot penetrate the object because of the ability of the material to absorb light and reflect it.
Why Do We Have Shadows?
As aforementioned, it is the region where electromagnetic radiation does not arrive here. Light moves in a straight line from a source and it also diverges as it propagates in the direction it is produced towards, so as we get farther away from the object we see a big shadow, because light must have diverged to a large extent by then.
The wavenumber of light moving normally per unit area earlier i.e., in the beginning, is greater than that in the greater distance, so because the light wave's flux is greater near the object in the beginning or at a shorter distance from the source, the number of light rays falling on the sides of the object is also high. There is a lot of contrast in the brightness of light and darkness of shadow, whereas at more distance the flux of light falling on the sides of the object is less than explained earlier but the darkness of shadow remains the same or decreases because of light reflected by different objects reaches the behind the object. Although considering an ideal case this does not happen, so the darkness remains the same as the light density covered by the object is the same in this case too, but the shadow looks dull as the light density falling on its sides is small and so the contrast within shadowed and brighter areas is less.
What Is The Color Of Shadows?
It depends on several factors, like; lighting, material color, reflectance, and proximity to other objects.
The common color for shadows is inherently blue when the light sources are the sun and the sky. In shadows, the blue sky is the main source of illumination.
Contrarily, the shadow will be the color of whatever light is still hitting it. Both cameras and our eyes tend to "white balance (WB)", so that should probably be taken into account.
If there are three light bulbs; red, green, and blue. You will see shadows with all the additive and subtractive primaries (green, red, yellow, magenta, cyan, blue). Shadows are a combination of an object's local color, illuminated by minor light sources, and reflections from the surrounding environment, and the shadow is not directly lit from the dominant light source.
