by Nancy Sutthoff
The Electromagnetic Spectrum
The entire electromagnetic spectrum is made up of
ultraviolet, visible light, and infrared. The human eye can only see the light
sector of the spectrum. That is
Red, Orange, Yellow, Green, Blue, Indigo and Violet. (ROY G BIV is how I
was taught to remember it in school).
These are also the colors you see in a rainbow after a rainstorm.
Color is the thing we perhaps notice most about light in
the world around us. But why we see colors the way we do all has to do with
light. The reason something appears to be the color that does is that the object
is absorbing all the other colors of light except the ones we see, which are
reflected back to our eyes. If something absorbs all the colors, it appears
black, if it reflects everything, it appears white. Color comes from what is
called the visible spectrum of light. Scientists
measure the wavelengths of light in this spectrum in nanometers or billionths of
a meter. Red has the longest wavelength, and violet has the shortest. So, what
color we see depends on the wavelength of the light we absorb into our eyes. The
primary colors are red, green, and blue, from these colors, every other color
can be made.
The ultraviolet and infrared are wave energy that can not
be seen by our eyes. William Herschel began down the road to discovering the
electromagnetic spectrum in 1799. He wanted to find out how light and heat were
connected. He used a prism to break up white light and used a thermometer to
measure the temperature of each of the different colors. Each color, he found,
did not have the same temperature. Red had the highest reading of all of the
colors, while violet gave the lowest.
However, past the red that we are able to see, Herschel
found something that was even hotter than red itself. This end of the
electromagnetic spectrum he called infrared. Infrared can be felt, but it can
not be seen by the naked eye. The wavelengths of the visible spectrum are all
medium in length. The wavelengths of infrared light are very slow. Everything
emits infrared light. Even things found in your freezer emit it. Infrared can be
found in anything above absolute zero. The amount of infrared light that an
object emits depends on its temperature. A human gives off much more infrared
light than an ice cube would. No matter what time of day it is, the same amount
of infrared light is given off. Because of this, movement can be detected in the
dark with infrared detectors. Some animals, like snakes of the pit viper family,
are able to pick up on infrared waves to detect their prey.
At the other end of the spectrum, past violet, is
ultraviolet. Ultraviolet was discovered by Wilhelm Ritter in 1801. He dipped
strips of paper into silver nitrate and shown certain types of light on them.
Silver nitrate goes under a chemical reaction when exposed to light, and Ritter
found that the reaction was different depending on the type of color that was
shined on it. When exposed to violet light, the paper would turn much darker
than any of the other colors. Knowing that Herschel had found unseen light at
the red end of the spectrum, Ritter decided to see if there was at the violet
end. When he did this, the paper turned darker than when exposed to violet
light, proving that there was light beyond violet. This invisible light was
named ultraviolet. Ultra violet light is often given off by the sun. Most are
reflected by the ozone layer, but some do get into our atmosphere. These rays
damage unprotected skin and have been known to cause skin cancer.
This is the light that gives you sunburn and this is the light that
sunscreen protects us from.
Just as with Light, Color is not as simple as it seems to
be at first thought. To find out
more about color, take a click over to the website listed below:
Color Matters how color affects us all