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Light
Light
is
electromagnetic radiation
within a certain portion of the
electromagnetic spectrum
. The word usually refers to
visible light
, which is
visible
to the
human eye
and is responsible for the sense of
sight
. Visible light is usually defined as having
wavelengths
in the range of 400–700
nanometres
(nm), or 4.00 × 10
-7
to 7.00 × 10
-7
m, between the
infrared
(with longer wavelengths) and the
ultraviolet
(with shorter wavelengths). This wavelength means a
frequency
range of roughly 430–750
terahertz
(THz).
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