It comes to us from the Sun in the form of invisible radiation. Weather reports now give warnings if the ultraviolet radiation will be strong. Always wear sunscreen to protect your skin if you will be outside. Sometimes the brain is deceived by information received from the eyes. Optical illusions are caused when differences occur between our perceptions or expectations and the image seen by the eye.
Perception is a combination of seeing with memory and imagination.
It means understanding the meaning of images seen by the eye and sent to the brain.