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The Eye: Vision

Spectrum of light - The electromagnetic spectrum is the spectrum of all forms of light across the many frequencies it travels at. The light we see is a small, slim sliver of the electromagnetic spectrum. It is significant to us, because it is through these few wavelengths of light all the richness of the world is conveyed to us. Light is Invisible if the wavelength is too short or too long.

Notes on the structure and function of the eye. eye

The Image is reversed in the eye, this is "fixed" by the brain.
Light waves must be focused to be seen. the Cornea focus the light waves into a narrower beam.
The Pupil allows light into the interior of the eye.
The Iris controls the amount of light allowed to enter.
The Lens focus, focus , focus
The Retina - begins transduction
The Eyeball's shape affects vision
     Nearsightedness - eyeball to long
     Farsightedness - eyeball to short
Retina: a miniature camera-computer has two types of photoreceptors:
     Rods to see in dim light
     Cones to see color
  Transduction (light to nerve impulses) occurs in the retina. The transmission path to the brain is the optic nerve. There is a blind spot where the optic nerve exits the eye but it is not noticed because the eye is constantly moving.
 Visual pathways: eye to brain
     - The optic nerve connects to the thalamus for initial processing. Next stop the occipital lobe.
     - The primary visual cortex in the occipital lobe using specialized cells adds detail.
     - The visual association areas in the occipital lobe add meaning and complete the process producing vision.

Color vision - theories

     The trichromatic theory of color vision is based on the premise that there are three classes of cone receptors serving color vision. One of the more important empirical aspects of this theory is that it is possible to match all of the colors in the visible spectrum by the appropriate mixing of the three primary additive colors red, green, & blue. When these are mixed equally white is produced.
    User Friendly   FYI: The three primary subtractive (pigment) colors are red, blue, & yellow. When pigment colors are mixed equally black is produced.
     The opponent-process theory
         Afterimages show opponent pairs: red-green & yellow-blue
         When excited or inhibited, ganglion & thalamic cells signal
         one of the pair colors.
     Physiology shows: Trichromatic + Opponent-processes are combined.
Color blindness
     Monochromats - no cones = no color
     Dichromats - cannot tell red from green

General Psychology
Robert C. Gates