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What is Light?
by Jeanette Cain
Early Greek scholars thought that a person's eyes sent light rays to shine on the object they were looking upon. Can this be true? If you sit in a room
completely without light and try to read a book, would you be able too?
The exact opposite is what really happens. Whatever we look upon must send out the light for us to see. If you're outside reading, the sunlight shines on the page and then bounces (reflects) into
your eyes. If you're sitting in your room reading a book with the light on, the light bounces (reflects) from your book to your eyes. Nerves within our eyes bring this image message, which is
then sent to our brain. That is how you are able to read!
Do the eyes of a cat really glow at night when hit with a beam of light? Cat's eyes do not send out rays of light. The mirror-like lining in the back of the cat's eyes simply bounces (reflects)
the light beam.
What do you call things that you see because they GIVE OFF their own light? Luminous. Luminous objects include the sun and an electric light bulb. The moon is not luminous, rather,
moonlight happens when light from the sun bounces off the moon.
Dark things usually soak up the light that falls on them with very little light bouncing off (reflected). That is why darker objects are harder to see. Light things bounce (reflect) more light.
What do you think one of the best bouncers (reflectors) of light would be? A sheet of glass with a light-colored, shiny coating on the back.
Light can be studied in physics. It is known as a spectrum.
Definitions:
Bounce: Means to throw out or throw back.
Light: Means that by which we see. It is a form of energy that acts on the retina in our eyes. It can be anything that gives light, such as a lamp, or the sun.
Physics: Means the science that deals in matter and energy. Studies in physics include light, sound, heat, electricity and mechanics.
Reflect: Means to throw or turn back, such as with light, heat and sound. It means to give back a likeness or image, such as a mirror.
Reference
Barnhart, Clarence L. Thorndike-Barnhart Comprehensive Desk Dictionary. Doubleday & Co. Inc.: NY. 1965
Helpful sites
Quantum Mechanics Made Simple
Students entry to the ThinkQuest Library. Available in English, French and Arabic. Designed to attract all levels of visitors - special emphasis on students.
Spectral Lines
Elemetary explanation of quantum atoms, emr's, light with interactive area. Good for the younger set - 10 and under.
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