The Spectrum of
Visible Light
The visible part of the spectrum may be further subdivided according to color, with
red at the long
wavelength end and violet at the short wavelength end, as illustrated
(schematically) in the
following figure.
The actual wavelengths corresponding to different colors in the visible spectrum are listed in
the adjacent table. Notice that the regions of the visible spectrum are not equally divided.
For example, the blue region is only about 40 nanometers wide, but red covers about 70 nm.
|
Colors of the Visible Spectrum
|
| Color |
Wavelength (nm) |
Wavelength (Angstroms)
|
| Violet |
400-440 |
4000-4400
|
| Blue |
440-480 |
4400-4800
|
| Green |
480-560 |
4800-5600
|
| Yellow |
560-590 |
5600-5900
|
| Orange |
590-630 |
5900-6300
|
| Red |
630-700 |
6300-7000 |
|
|
|
|
|
Roy G. BV
The sequence of colors red, orange, yellow, green, blue, and violet may be
remembered by
memorizing the name of that fine fellow "ROY G. BV".
This
animation
illustrates the visible
spectrum.
Roy's name at one time was "ROY G. BIV", because it used to be common to call the
region between blue and violet "indigo". In modern usage, indigo is not usually
distinguished as a separate color in the visible spectrum. So Roy no longer has any
vowels in his last name.
Visible Light and Human Eyes
The normal human eye is sensitive to the full range of the visible spectrum, but
not equally sensitive. The eye is more sensitive to the yellow and green regions
in the center, with the sensitivity dropping off as the wavelength increases toward
the red or decreases toward the violet.
The Sun produces its primary light output in the yellow portion of the spectrum.
Thus, it is probably not surprising that life forms
evolving under the influence of that
Sun developed eyes that are sensitive to yellow light.
