Why is the sky blue? Why sunsets are orange -red? « Back to Questions List



The light coming from the sun is white. This white light is made up of all colours of the rainbow. Like energy passing through the ocean, light energy travels in waves, too. Some light travels in short, "choppy" waves. Other light travels in long, lazy waves.  Violet and blue light has shorter wavelengths, while red light has a longer wavelength, and the other colors have wavelengths in between.


prism   prism1





§  reflect it (like a mirror)

§  bend it (like a prism)

§  or scatter it (like molecules of the gases, water droplets, dust etc   in the atmosphere)


Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. These particles scatter violet and blue light much more than red, and so they send rays of violet and blue toward the ground — and our eyes. More violet light actually gets scattered by atmospheric particles than blue light, but our eyes are more sensitive to blue, so the sky appears blue.





Sunsets are orange-red because in the evening, with the sun low on the horizon, sunlight must pass through more atmosphere to get to your eyes, and only the red light can make it all the way through. The shorter wavelengths have all been scattered toward the ground in the part of Earth where it is still daytime.