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Our eyes
can detect only a tiny part of the electromagnetic
spectrum, called visible light. This means that there's
a great deal happening around us that we're simply not aware
of, unless we have instruments to detect it.

Light waves are given off by anything
that's hot enough to glow. This is how light bulbs
work - an electric current heats the lamp filament to around
3,000 degrees, and it glows white-hot.
The surface
of the Sun is around 5,600 degrees, and it gives off a great
deal of light. |
Cinema projectors
use a powerful lamp |