While it is true that shadows are created by the absence of light, you can still see objects within shadows due to the way light interacts with the surrounding environment. Here's an explanation of why you can perceive objects in shadows:
Diffuse Reflection: When light encounters an object, it can undergo two types of reflection: specular reflection and diffuse reflection. Specular reflection occurs when light bounces off a smooth surface, like a mirror, in a predictable manner. However, objects typically have rough or uneven surfaces, causing light to undergo diffuse reflection. In diffuse reflection, light scatters in various directions upon hitting the object's surface.
Ambient Light: Even in areas that appear to be in shadow, there is often ambient light present. Ambient light is the general illumination in an environment that comes from various sources, such as indirect sunlight, artificial lighting, or light reflecting off surfaces. This ambient light can enter the shadowed area from different directions, indirectly illuminating objects within the shadow.
Indirect Light: Light can also be reflected or refracted around objects, reaching areas that are not directly exposed to the primary light source. For example, light can bounce off surfaces surrounding the shadowed area and indirectly illuminate the objects within the shadow. This indirect light helps reveal the objects' shapes and forms even though they are not directly lit by the primary light source.
Adaptation of Eyes: Our eyes are remarkably adept at adjusting to different lighting conditions. They can adapt to varying levels of brightness, allowing us to perceive objects within shadows by making use of the available light. Our visual system can enhance contrast and sensitivity in low-light situations, making objects in the shadowed areas more discernible.
By considering these factors - diffuse reflection, ambient light, indirect light, and the adaptation of our eyes - we are able to see objects within shadows, even though shadows are technically areas with less light compared to their surroundings.