Tyndall Effect
from McGraw-Hill Concise Encyclopedia
of Science and Technology, 1984
Tyndall Effect: Visible scattering of light along the
path of a beam of light as it passes through a system
containing discontinuities. The luminous path of a beam
of light is called a Tyndall Cone. In colloidal systems the
brilliance of the Tyndall Cone is directly dependent on the
magnitude of the difference in refractive index between
the particle and the medium.
For systems with particles with diameters less than one-
twentieth the wavelength of light, the light scattered from
a polychromatic beam is predominantly blue in color and
is polarized to a degree which depends on the angle
between the observer and the incident beam. The blue
color of tobacco smoke is an example of Tyndall blue. As
particles are increased in size, the blue color of scattered
light disappears and the scattered radiation appears white.
If this scattered light is received through a nicol prism
which is oriented to extinguish the vertically polarized
scattered light, the blue color appears again in increased
brilliance. This is called residual blue, and its intensity
varies as the inverse eighth power of the wavelength.
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