Why sky is blue ?
When we see a rainbow we can see a range of colours from red (longer wavelength) through yellows and greens to blues and eventually violet (shorter wavelengths). So if shorter wavelengths are more easily scattered why don’t we see the sky as purple?
The answer lies with how our eyes react to light. Inside the eye there are two types of cells that react to light. ‘Rods’ are sensitive to brightness and three types of ‘cones’ are responsible for detecting colour. The three types of cones are sensitive to lights of certain wavelengths.
The ‘blue’ cones are more sensitive to blue than violet, so when you look up at the sky, the cones tell your brain you are seeing blue even though there is violet there.