Electromagnetic Spectrum

Do you listen to the radio, watch TV, or use a microwave oven? All these devices make use of electromagnetic waves. Radio waves, microwaves, visible light, and x rays are all examples of electromagnetic waves that differ from each other in wavelength.

(a) Longer wavelength; (b) shorter wavelength.

Electromagnetic waves are produced by the motion of electrically charged particles. These waves are also called "electromagnetic radiation" because they radiate from the electrically charged particles. They travel through empty space as well as through air and other substances.

Scientists have observed that electromagnetic radiation has a dual "personality." Besides acting like waves, it acts like a stream of particles (called "photons") that have no mass. The photons with the highest energy correspond to the shortest wavelengths.

The full range of wavelengths (and photon energies) is called the "electromagnetic spectrum."

The electromagnetic spectrum covers a wide range of wavelengths and photon energies. Light used to "see" an object must have a wavelength about the same size as or smaller than the object. The ALS generates light in the far ultraviolet and soft x-ray regions, which span the wavelengths suited to studying molecules and atoms.

Look at the picture of the electromagnetic spectrum. See if you can find answers to these questions:

  1. What kind of electromagnetic radiation has the shortest wavelength? The longest?
  2. What kind of electromagnetic radiation could be used to "see" molecules? Quarks?
  3. Why can't you use visible light to "see" molecules?
Some insects like bees can see light of shorter wavelengths than humans can see. What kind of radiation do you think a bee sees?

For more information, go to "How Is Seeing Related to Wavelength?"

Return to "The Advanced Light Source: A Tool for Solving the Mysteries of Materials."