refraction

321

These rainbows are caused by some of Nancy's prisms. Why is there no green in these rainbows?

323

The colors of a butterfly's wings are caused by tiny scales. Do they all produce colors in the same way?

414

I took this photo on a boat excursion on the Colorado River. A recent comment asked why the sky is blue. OK, so why is the sky blue? And why is it bluer on some days and less blue on others?

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