Caption: The visible band of the electromagnetic spectrum illustrated.

Features:

1. The visible band (fiducial range 0.400--0.700 μm = 400--700 nm) is that region of the electromagnetic spectrum to which the human eye is sensitive.

2. The psychophysical response of the human eye to varying wavelength in the visible band is color.

3. The image illustrates the visible band approximately via the spectrum obtained by dispersion of ordinary white light. Actually, this spectrum seems to be synthetic and NOT an actual image.

4. The visible band is conventionally divided into 6 color bands:
   1. violet color band (fiducial range 0.380--0.450 μm)
   2. blue color band (fiducial range 0.450--0.495 μm)
   3. green color band (fiducial range 0.495--0.570 μm)
   4. yellow color band (fiducial range 0.570--0.590 μm)
   5. orange color band (fiducial range 0.590--0.620 μm)
   6. red color band (fiducial range 0.620--0.740 μm)

5. There are actually NO sharp divisions between the human eye's perception of color which is why the color band specifications are conventional.

6. The spectral colors are NOT the only colors.

   Other colors can be created by mixing wavelength bands that are adjacent or non-adjacent.

   Non-spectral colors include for example:

   1. white light: made by various mixtures from the visible band. The prototype white light is sunlight which is approximately a blackbody spectrum of temperature 5772 K (which is the effective temperature of the solar photosphere: see Wikipedia: Sun). Incandescent light bulbs (temperature range ∼ 2000--3300 K) (Wikipedia: Incandescent light bulb: Construction) produce white light to psychophysical response using blackbody spectra, but with a much lower temperatures than sunlight. White light LEDs produce white light to psychophysical response, but their spectra are NOT blackbody spectra. Good white light LEDs somewhat fool the human eye although some people find them somehow NOT right.
   2. black: in pure form is NO visible band light at all. But why does our psychophysical perception of zero light look black?
   3. brown: a composite color made from visible band containing long wavelength (low frequency) hues of yellow, orange, and red in varying amounts and having low luminance (in psychophysical perception brightness) or low colorfulness (see Wikipedia: Brown: Optics). Since brown vareis widely, composite adjectives are often applicable: e.g., red brown, yellowish brown, dark brown or light brown. Different art media have their own recipes for brown (see Wikipedia: Brown).
   4. magenta: a mixture of violet/blue and red.

7. Actually, humans can see a bit beyond the fiducial visible band = 0.4--0.7 μm:
   EOF