World Book Trivia Challenge Advanced--1/7--colours

The eyes of certain other animals are sensitive to light that we cannot see. For example, bees can see ultraviolet rays, which are invisible to people. On the other hand, bees cannot see the light that we see as red.

Artificial vision is the use of special technology to give some vision to people without natural sight. Devices for artificial vision are largely experimental. However, scientists are working to develop functional models that will give some vision to certain people who would otherwise be blind.
The image created by a retinal prosthesis appears as a pattern of lighted dots that are large and fuzzy. The retinal prosthesis cannot create a detailed picture, but it may help a blind person, for example, to find his or her way around obstacles and to locate objects at close range.

In patients with damaged optic nerves, signals cannot get from the eye to the portion of the brain responsible for vision. In these patients, physicians can implant electrodes directly in the brain to receive signals. In combination with an external camera and a computer, the electrodes stimulate brain cells to produce a crude image.

Colour blindness is usually inherited. It may also be acquired as a result of eye disease or an injury to the brain. Of the inherited forms, red-green colour vision defects are the most common. If a colour-blind man marries a woman with no family history of colour blindness, their children will have normal colour vision. If a woman whose father is colour blind marries a man with normal colour vision, each of the sons has a 50-50 chance of inheriting the defect.

The retina of a person with normal colour vision has three types of cones. One type responds most strongly to light of short wavelengths, which corresponds to the colour blue. Another type reacts chiefly to light of middle wavelengths, or green. The third type is most sensitive to light of long wavelengths, or red.

Colour blindness, sometimes called colour vision deficiency or Daltonism, is the inability to tell certain colours apart. The ability to see colour originates in specific visual cells, called cones, in the retina.

The characteristics of colour are (1) hue, (2) lightness, and (3) chroma. Colour experts describe an object's colour in terms of these characteristics.

Every colour has three basic characteristics. They are (1) hue, (2) lightness, and (3) chroma. Colour experts describe an object's colour in terms of these characteristics

Empedocles, a Greek philosopher of the 400's B.C., believed that colour vision was caused by tiny particles that were given off by objects and passed through the eyes. He thought that the eyes either produced a colour reaction to the particles or recognised them as coloured. In the early 300's B.C., the Greek philosopher Plato proposed that colour vision was caused by rays that shot out from the eyes toward objects. Aristotle, a Greek philosopher of the later 300's B.C., may have been the first person to realize that there is a relation between colour and light

Experts estimate that we can distinguish perhaps as many as 10 million colours. Each colour differs from all others in some degree of hue, lightness, or chroma. Our names for colours are far too inexact to describe accurately all the colorus we see