How do people see?


Quick Answer

Vision works by collecting visible light from the environment and transmitting information about that light to the brain. For vision to be meaningful to the human brain, the information it receives must then be processed into images that make sense in the context of how the brain perceives the world.

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Full Answer

The sun emits light with a peak energy in the middle of what humans know as the visible-light range of the spectrum, which is approximately on the yellow-green band. This light strikes surfaces on Earth and is either absorbed, scattered or reflected. Some of the light that is reflected off of surfaces enters the eyes, passing through the lens of each eye and focusing on an area at the back of each eye called the cornea. When an image reaches the cornea, it is inverted and two-dimensional. The cornea is densely packed with nerve endings and special cells called photoreceptors. Photoreceptors have a specialized protein in them, called rhodopsin, which becomes excited when struck by a photon. The excited protein briefly emits an electrical discharge that travels up the optic nerve to the occipital cortex at the back of the brain, where images from both eyes are superimposed to give them depth. From there, image data is distributed throughout the brain to compare received images to what are essentially stock images stored in the memory, which gives the brain the necessary context to understand what the eyes are looking at.

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