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What is Light?

by Nancy Sutthoff

If you were to ask someone the above question they may well look at you as if you were either joking or just a bit nutty. They may even tell you they think you are. That is fine. They will not have read this article so therefore, they may think they know what light is, but they won’t have the whole story. You will.

Light is not as simple as it seems to be.

Since the beginning of time, humans have strived to discover and understand what light is exactly. In simple terms, light is energy. Therefore, scientists who study light are called Physicists. Physics is the study of energy and matter. The effects of energy on matter, and the effects of matter on energy.

Sunlight/Solar Energy

The light we receive in the form of daylight from the sun is officially called Solar Energy. Solar energy also provides food for the Earth. This is how: Light from the sun contains a vast amount of energy that, if tapped into, has a great deal of power to be obtained. From the very beginning plants have used the sun to create energy. Animals such as reptiles use it to maintain their body temperature. We humans have only recently begun to explore the potentials of one of the most valuable resources available to us; the sun.

Plants use light to make their own food. Plants are also known as autotrophs, which means they are able to make their food from the light of the sun. They make their food through a process called photosynthesis. Through photosynthesis, plants are able to take the energy from the sun's rays and turn it into a type of energy that they are able to use. All green plants use this method. Some bacteria are also known to use photosynthesis.

Color

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. This spectrum goes from red to orange to yellow to green to blue to indigo to violet, all the major colors of the spectrum, and everything in between. An easy way to remember this order is to remember Roy G. Biv, much liked the colors of the rainbow. 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 of light differ from the primary colors of solid objects such as paint (red, blue and yellow). The primary colors of light are blue, green, and red. From these colors, every other color can be made.

Activities:

  • Draw a rainbow, or use a prism to create a miniature rainbow that you can observe.
  • Get three flashlights, and cover the ends with red, blue, and green cellophane. Shine different combinations of light on a piece of white paper and see what colors you get.
  • Find out if your town uses and/or has facilities to make solar energy usable for utilities (electricity, heat, water). If so, see if they offer tours of the premises so you can SEE how light is energy.
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