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The thin film effect refers to colors seen in
such things as soap bubbles and oil spills. It
occurs as a result of the constructive and
destructive interference of light waves, not
because of refraction as in a prism. When light
hits a bubble, some of it is reflected by the
outer (air-soap) interface (ray #1), while some
penetrates the bubble wall and is reflected by
the inner (soap-air) interface (ray #2). The two
reflected rays interfere with one another.
Typically, most wavelengths will be out of
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phase since #2 has to travel a greater
distance than #1. However, one wavelength will be in
phase and this corresponds to the color produced.
The color depends on how great the difference in
distance is that the two rays travel, and this distance
depends on bubble thickness. The variations in
reflected thickness (thinner at the top, thicker at the bottom)
are responsible for the different colors.
Continued on Next Soap Bubble Wall Thin Films (cont.) When light moving through the air encounter...
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