Submodule 3: Color and the Spectrum
Steve Beeson, Arizona State University

What other kinds of "light" are there?

Our world is alive with color, shadows, and beauty. We're able to see a huge variety of objects all around us, and we often think that if we don't see something, it's not there. However, as scientists realized in the late 19th century and early 20th century, there is much more to the world than we can perceive. Compare, for instance, the painting of A Young Girl Reading, by Jean-Honoré Fragonard, seen in two different kinds of "light": visible light (to which our eyes are sensitive) and X-rays.

Light is only a small part of the electromagnetic spectrum, the broad range of energies which are produced when electrical charges are accelerated. A small piece of this energy is called a photon, a "light particle" which carries the energy. We can also think of this energy being carried by a wave, with a specific wavelength or frequency. Either way of thinking of light, as a particle of energy (a photon), or a wave carrying energy, is correct and useful.

Most of the electromagnetic spectrum is not accessible to us, unless we're aided by special detectors tuned to the desired energies, much like our eyes are "tuned" to the energy of visible light. Let's "look" at some of the other portions of the spectrum and "see" how they play a part in our lives. Click on the area of the spectrum below that you would like to visit.

Please note that the boundaries of the regions in the electromagnetic spectrum are in no way as sharp as the diagram suggests. For instance, the distinction between ultraviolet light and X-rays is not clearly defined: one person may consider a highly energetic photon an X-ray while another might consider the same photon an ultraviolet photon.

To learn more about photons and the electromagnetic spectrum go to the Color and Light readings.

Light & Optics
Submodule 3
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Copyright &copy1995-1997
Steve Beeson, Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287