How Black is Black?

1
How Black is Black?
The colors perceived by our eyes are a small part
of the electromagnetic spectrum.
The physical approximation to a blackbody is a
cavity with a small aperture and large internal
surface area. We want our ACR cavity to be as
close to a blackbody as possible.
Many internal reflections within the cavity
absorb input radiation. The more absorptive the
cavity surface, the better the blackbody
approximation.
To our eye, black is simply an lack of
wavelengths in the visible spectrum.
A true blackbody perfectly absorbs radiation and
characteristically re-emits radiative energy.
With many internal reflections, a cavity coated
with reflective white paper can look blacker to
our eye than a sheet of black paper!
References https//www.glenbrook.k12.il.us/qbssci
/phys/Class/light/u1212a.html http//lasp.colorado
.edu/cassini/questions/Electromagnetic20Spectrum.
htm