1828: Nicol prism - The book of science

Nicol prism
Famous prisms
Secondary qualities
Commentary

Nicol prism

Rasmus Bartholin understood
that Iceland spar, a transparent calcite crystal,
produces a double refraction, that is, birefringence.
Viking navigators called these “sunstones”
and used them to discern
the direction of the sun on cloudy days.
William Nicol constructed a prism
by gluing together two pieces of Iceland spar
cut at exactly 68 degrees to the crystal axis.
Nicol’s prism produces a plane polarized light,
correcting the refraction of the extraordinary ray
and eliminating the ordinary ray by internal reflection.

Famous prisms

Isaac Newton used two triangular glass prisms
to discover his theory of color.
Augustin-Jean Fresnel used circular arrays
of curved glass prisms to concentrate a lighthouse beam.
Ignazio Porro used a double Porro prism
in his prism binoculars.
Giovanni Battista Donati used a double-Amici prism
to observe stellar spectra.
Leonard R. Ingersoll used a Nicol prism
in his Glarimeter to measure paper glossiness.

Secondary qualities

What we perceive
as through a sieve
reflects bio-specifics
more than physics.

If, by the term “color,” we mean a combined set of different frequencies of light, then we are talking about physics. But if we mean a combined sense of degrees of red, blue, and green, then we are talking about perception. Newton’s experiment was the first to pry physics from perception, and Nicol’s prism was the first to provide plane polarized light.