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What optics principle is responsible for the colored fringes seen in the attached picture?strands of hair reflecting sunlight when held very close to the lens[pic 2]1]1

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The colored fringes are probably due to a combination of diffraction and dispersive refraction, along the lines of how rainbows are formed by light scattering from water droplets in the air.

It's worthwhile to read the Wikipedia article on rainbows. Note that "supernumerary rainbows" depend on interference.

The details of the color pattern you see in each "blob" in your photo are dependent on the orientation of the hairs, the position of the light source, the size and detailed shape of the hairs, and the distance of the hair from the lens. If you really want to explore this effect, you could try setting up a spotlight for controlled illumination, put the hairs in a holder so they will stay still, and move the camera lens closer and farther away along a linear track so you can see how the lens-to-hair distance affects the pattern. You might mount a hair vertically on a rotational mount and rotate it to see if and how the colors shift. See if a very fine thread of glass, plastic, or sugar (cotton candy) does the same as a hair. And so on.

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  • $\begingroup$ Thanks. That gives me some insights. $\endgroup$ – Swap Dec 16 '19 at 22:37

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