When we look at an object, we perceive it by detecting and interpreting the light that is either emitted or reflected by the object.
In the case of an object that emits light, such as a glowing light bulb, we see the object directly because the light is emanating from the object itself. Our eyes detect the light rays emitted by the object, and our brain processes this information to form our perception of the object.
For objects that do not emit their own light, such as a book or a tree, we see them due to the reflection of light. When light from an external source, such as the Sun or a lamp, falls onto the object's surface, it interacts with the material of the object. The atoms or molecules in the object absorb some of the incoming light and re-emit or reflect the remaining light. This reflected light then enters our eyes, where it is detected by our retinas, and our brain processes this information to create the visual perception of the object.
So, in the case of objects that do not emit their own light, we see the object through the reflection of light from its surface. Our perception is based on the interaction between light and the object's surface, and the resulting reflected light that reaches our eyes.