Why is the sky blue? science and knowledge!

Why is the sky blue?
Earth's atmosphere contains a small gas molecules and particles (grains) dust. Sunlight enters the atmosphere met with gas molecules and dust particles before. The color of light has a wave length of light is more like red and yellow, the molecules can pass through and penetrate the gas and dust earlier. But the color blue has a shorter light waves reflected back to the top of the atmosphere. That is why the sky looks blue?. The same principle valid also to the water in a sea or lake that looks blue.