Re: The Wavelength of light
A 6th Grader Asks About Light
Phil Schewe of the American Institute of Physics Replies
Date: Fri, 1 Jan 1999 14:28:48 EST
Subject: A physics question
What is the WAVELENGTH of light
Hi: my name is Aliza and I am in 6th grade.
I am doing a science fair report on Light and Color. I have looked in many
dictionaries and glossaries and I can't find a definition of WAVELENGTH that I understand. Could you possibly explain, in words that I can understand, what it means for light to have a wavelength.
Please respond ASAP.
The Answer (We passed this question to the American Institute of Physics, where Phil Schewe kindly provided this response.)
A lot of things in
nature consist of waves: waves going across an ocean, light waves, sound
waves, and waves in a jump rope. And it's handy to define two terms to
describe the waves. Waves are really pulses of energy moving through
space, and the energy can cause crests (an ocean wave at its height, or the
point where the jump rope is at its highest) with troughs in between (the low
points of an ocean wave or the low point of a jump rope).
Now for the definitions: (1) the wavelength of the wave is the distance
between crests--for an ocean wave it might be 20 feet, for a jump rope 1
foot. (2) The frequency of the wave is the number of crests that pass every
second. The jump rope might have a frequency of a few per second. For
sound, where the waves consist in alternating bands of high pressure (the crests) and low pressure traveling through a medium, such as air, water or steel, the frequency might be thousands.
Light is a trickier wave to describe since light is made up of little
electrical forces (the force that makes electrons go through your toaster or
TV) and magnetic forces (the forces that hold a magnet onto your
refrigerator). But it's still true that the lightwave has crests and
troughs in between. But the wavelength of visible light (the light you can
see with your eyes) is very small: twenty million of them could fit itside a
There are other kinds of light we can't see, such as x-rays, with a
wavelength about the size of an atom, and radio waves, with wavelengths
greater than the size of a house.
I hope this answers your question.
Sincerely, Phillip F. Schewe
American Institute of Physics
One Physics Ellipse
College Park, MD 20740
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