Module 1.6b - Sensation: Vision

Wavelength

The distance from the peak of one light wave or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short gamma waves to the long pulses of radio transmission.

Hue

The dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth. 

Intensity

The amount of energy in a light wave or sound wave, which influences what we perceive as brightness or loudness. Determined by the wave’s amplitude (height)

Cornea

The eye’s clear, protective outer layer, covering the pupil and iris. 

Pupil

The adjustable opening in the center of the eye through which light enters.

Iris

A ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina.

Retina

The light-sensitive back inner surface of the eye, containing inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin processing visual information.

Accommodation

The process by which the eye’s lens changes shape to focus images of near or far objects on the retina.

Rods

Retinal receptors that detect black, white, and gray,, and are sensitive to movement. are necessary for peripheral and twilight vision, when cones don’t respond.

Cones

Retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. detect fine detail and give rise to color sensations.

Optic nerve

 The nerve that carries neural impulses from the eye to the brain.

Blind spot

The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.

Fovea

 The central focal point in the retina, around which the eye’s cone cluster.

Young-Helmholtz trichromatic (three-color) theory

 The theory that the retina contains three different types of color receptors –one most sensitive to red, one to green, one to blue–which, when stimulated in combination, can produce the perception of any color.

Opponent-process theory

The theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

Feature detectors

Nerve cells in the brain’s visual cortex that respond to specific features of the stimulus, such as the shape, angle, or movement.

Parallel processing

Processing multiple aspects of a stimulus or problem simultaneously.