Sensing Light Images
Vision begins when light enters the eye and forms an image on the retina, which converts it into nerve signals that the brain interprets as what we see.
Questions you may have include:
- How does the eye sense light?
- How is an image formed?
- How do we see color?
How the eye senses light
Light passes through the cornea and the lens, which focus it onto the retina at the back of the eye. The lens adjusts its shape to focus on objects at different distances.
Forming an image
The retina is lined with light-sensitive photoreceptor cells. Rods are very sensitive and work in dim light but do not detect color; cones work in brighter light and provide color and detail. The focused image actually lands upside down, and the brain interprets it the right way up.
Seeing color
Color vision comes from three types of cone, each most sensitive to a different range of wavelengths — roughly red, green, and blue. The brain combines their signals to produce the full range of colors we perceive.
Summary
Vision works as the cornea and lens focus light onto the retina, where rods detect dim light and cones detect color and detail. The brain interprets these signals — including combining three cone types for color — into the images we see.