Why can people see with their eyes?

The reason why people's eyes can see all kinds of things is that objects can reflect light in all directions after being irradiated by light, and when these reflected lights reach the eyes, we can see things through their unique functions. If there is no reflection of light in the dark, the eyes can't see.

Interestingly, not only human eyes and many creatures in nature can feel light, but also some metals have this ability to feel light. This metal can emit electrons under the irradiation of light. The stronger the light, the more electrons are emitted. Electrons flow in a conductor to form an electrical signal. This phenomenon is called photoelectric effect.