Question

Question #b50ce

Answer 1

The sky is violet, but violet (in the UV region, `"200~400 nm"`) is outside the visible wavelength region (`"400~700 nm"`). Therefore, the color of the next-shortest wavelength is more easily seen instead---blue.

Explanation:

See also: What color is the sky?

The human eye is very sensitive to light in the middle of the so-called visible spectrum. We see yellows and greens, even when they are at very low intensities. But in the very deep red or at the violet end of the spectrum (near `700` or near `"400 nm"`, respectively), it takes much more light be trigger a response in the human retina.

So, while there really is more violet light scattering through the air particles in the sky, the blue color is seen more easily.