What would you say if Bill Nye asked you - Why is the sky blue? See the response as the Science Guy strolls down Hollywood Blvd.
Ever been caught off guard when that little person next to you looks up in earnest and says, "Why is the sky blue?" This ought to help you get it right!
The light from the sun looks white, but its really made up of all the different colors of the rainbow. We can see this by using a simple prism and separating the light into its individual colors.
Just like energy and sound, light travels in waves. Some are short and choppy, while others are long and lazy. Blue light waves are shorter than red light waves. All of these light waves travel in straight lines unless something gets in the way and either reflects, bends, or scatters it.
As sunlight reaches Earth's atmosphere, it is scattered in all directions by the gases and particles in the air. Blue light is scattered more because it travels in shorter, smaller waves.
Closer to the horizon, the sky usually looks lighter blue or white because the sunlight has been scattered and reflected and mixed with other light from the surface of the earth that we see less blue and more white.
For more information, check out Science Made Simple: Why is the Sky Blue? and try this experiment.
Splitting Light
What you need:
a small mirror, a piece of white paper or cardboard, water
a large shallow bowl, pan, or plastic shoebox
a window with direct sunlight coming in, or a sunny day outdoors
What to do:
Fill the bowl or pan about 2/3 full of water.
Place it on a table or the floor, directly in the sunlight. (Note: the direct sunlight is important for this experiment to work right.)
Hold the mirror under water, facing towards the sun.
Hold the paper above and in front of the mirror.
Adjust the positions of the paper and mirror until the reflected light shines on the paper.
Observe the colored spectrum.
What happened: The water and mirror acted like a prism, splitting the light into the colors of the spectrum. When light passes from one medium to another, for example from air to water, its speed and direction change. The different colors of light are affected differently. Violet light slows the most, and bends the most. Red light slows and bends the least. The different colors of light are spread out and separated, and we can see the spectrum.
