Interference Colors, Tape Wedge
These are the interference colors shown by successive
layers of a plastic tape with a retardation of approximately 24.5
nanometers per layer when viewed between crossed polarizing filters. The successive
layers of tape can be counted by the
successive serrations at the end of each layer. There are approximately 44 layers of
tape at the extreme left side of the
image and the color seen there corresponds to a retardation of approximately 1078
nanometers (44X24.5). The first layer
is just barely visible at the extreme right of the image, the color that corresponds
to a retardation of 24.5 nanometers.
Transmited Crossed Polarized Light Macrophotograph
Definition/Function:
Interference colors can be created by viewing a material that has a regular asymmetry in
its molecular structure between polarizing filters.
"Crossed Polars" means that the two polarizing filters are in an orientation that
prevents any direct light from passing through the two filters.
If a material with aligned molecules or with a crystal structure other than cubic is
placed between the two filters in this orientation then
interference colors become visible. The color depends on the structure in the material
and the thickness of the material. The structure of the
material can be characterized by the maximum and minimum refractive index of the
material. These two refractive indices are always at 90 degrees
to one another. The difference between these two, maximum minus minimum, is the
"birefringence" of the material. The birefringence times the
thickness is the "retardation".
Significance in the Environment:
Characteristic Features:
Associated Particles:
References:
