Light, prism and the rainbow: What is Light ? Part 2
by Jeanette Cain
One of the most important experiments on light was made by Isaac Newton. He was the greatest of all English men of science. He discovered that
sunshine (white light) is made up of many colors. Over 300 years ago, Sir Isaac Newton passed a beam of white light through a prism. A prism is a triangular piece of glass, which
allows light to spread out into a band of six colors. These colors are red, orange, yellow, green, blue and violet. Newton then sent this light through a second prism where the light became white
once again. What did Sir Isaac Newton do? He first took the white light apart and then he put it back together again.
The most common example of a spectrum is the rainbow created in nature.
The rainbow is caused by sunshine (white light) shining on water droplets that are in the air just after a summer shower. Thousands of these water droplets break up the light, just like Sir Isaac
Newton's prism. Can you make a rainbow? Of course! Make your own rainbow by turning on the garden hose, which has a nozzle that will make a fine mist, or spray. Make sure the sunlight is coming
over your shoulder. You have made a rainbow.
What is light? Does it travel from place to place? Sir Isaac Newton thought that light was made of tiny particles that flowed in a stream from a light source. Other scientists argued that light
traveled in waves, like waves you see when tossing a rock into a lake, or pond. What do scientists today believe? Most believe that both ideas are right.
Lights acts as a stream of particles and as waves. It is made of tiny packets of energy calledphotons. Light is made of various waves, but the length of these waves determine the
color of light. Violet has about 70,000 waves to the inch and red light has about 40,000 waves to the inch. Where will you find the other colors? All the other colors are in between the light
spectrum.
We do not know of anything in our universe that travels faster than light. The sunlight we see today left the sun 93 million miles away to reach us about 10 minutes later. Light from stars
farther away may have taken billions of years to reach our eyes. How many times can light travel around the world while you are saying your name? More than four times.
There are colors which are invisible. These are called infrared and ultraviolet. The human eye is unable to see these colors, but science has special photographic films which can see
them.
Definitions
Beam: A beam may be timber, metal, or stone. When talking about a beam of light, we mean rays of light, a ray, or heat.
Prism: When working with light rays, a prism is transparent, usually with three-sided ends. It's shaped like a triangle. It separates the white light passing through into the colors of the
rainbow.
Spectrum: This is all of the colors that are formed when passing through the prism, and some other means.
Length: This is the measurement of an object or thing from one end to the other end. It is the longest way a thing can be measured.
Sources:
Barnhart, Clarence L. Thorndike-Barnhart Comprehensive Desk Dictionary Doubleday ∓ Company, Inc: NY. 1965
Editors. The World Book Encyclopedia. World Book-Childcraft International, Inc: Chicago. 1980
Miami Museum of Science - The Atoms Family: Dracula's Library
Experiments using mirrors and other reflectors: Radiometer - Grades 8-12; Afterimage - Grade 5-12; Reflections - Grades 5-12.
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