Origin of the colors

Basically, these so called structural colors might be derived from two different mechanisms, one of them is film interference of light and another is grating diffraction of light. If you are not familiar with those terms, you can read the detailed descriptions on wikipedia.org

In simple words, film interference of light will happen with a single layer film, or multi-layer films, with the thickness comparable with the wavelength of visible light (400-700nm). When the light beam is reflected by the top surface of the film and by the bottom of the film, these reflected lights will interfere with each other. Sometimes, the reflected light will be enhanced at certain wavelength, when the light path satisfies the film interference equation. When this happens, the film will appear a certain color corresponding with the wavelength. Examples of film interference include color of soap bubbles, oil film on water, and the color of camera lens glass.

Grating diffraction of light happens when the grating period distance is comparable with the wavelength, and satisfies the grating diffraction equation. This mechanism is responding for the colors on bird feather, butterfly wings, CDs and the dove image of on your visa credit card.

With the basic knowledge, now we will continue to examine the microstructures of the colorful meat to see what is going on there.....

 

Fig. 1. Diagram illustrating the light path in (a) single layer thin film interference; (b) grating diffraction.

References:

[1] http://en.wikipedia.org/wiki/Thin-film_interference

[2] http://en.wikipedia.org/wiki/Diffraction_grating

[3] S. Kinoshita et al.,Structural Colors in Nature: The Role of Regularity and Irregularity in the Structure. Chem Phys Chem 2005, 6, 1442 – 1459

 

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