Visual Light

Wavelength: 3.5 × 10-7m to 7.5 × 10-7m Sources: Very hot bodies (progressively red-hot, yellow-hot and then white-hot),

discharge lamps (eg, most bulbs), phosphorence and fluorescence of other types

of electromagnetic radiation into visible light. Detection: Photographic plates, photocells, the human eye. Uses: Cathode ray tubes, which emit light, are used for televisions, computer

monitors and the like. LED displays are used for cheap low resolution visual

information. LCDs use the reflection of light for a similar goal. Bulbs are

used for lighting which human beings and other animals then use as an aid for

(amongst other things) location resolving, navigation, communication, and

peripheral/accessory movement (eg, lifting cups of tea). Apart from all the everyday types of visual

communication there are a few other less obvious uses for visible light (which

do not depend on it’s visible to humans property). One is for

high-speed fibre optic links, where red light lasers, green light lasers and

(in the future) blue light lasers can carry digital data across long distances

at very high speed. With the emergence of the internet these high-bandwidth

solutions hold the key to global information sharing since the current

infrastructure is not be capable of sustaining the emerging traffic. Comments: The label "Visible" light demonstrates the ego-centricity of the

human race. The short side of infrared and the long side of ultraviolet are

separated by an extremely short band (relatively speaking) of radiation which

is detectable by the human eye. It is unlikely that another race of intelligent

beings, if it had a different natively "visible" section, would

highlight the small part between the infrared and ultraviolet as being

important.