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Figure 1: Explanation of thin-film interference. When the phase difference between the two reflected beams is an even integer multiple of the wavelength of the beam in the film, then the two reflected beams tend to interfere constructively. If the phase difference between the two reflected beams is an odd integer multiple of the wavelength of light in the film, the beams interfere destructively. |
Figure 2: Light path in a thin film of the metal's oxide. |
Tempering vs. Coating
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Coating
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differs from tempering in that it is used to render a relatively thick medium that has been applied on top of the metal (such as is the case of car paint). Tempering produces a very thin layer of oxyde on the metal surface which can produces interference.
Anisotropy
From Wikipedia: "In the field of computer graphics, an anisotropic surface changes in appearance as it rotates about its geometric normal, as is the case with velvet".
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