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• Words to Know

The term spectrum has two different, but closely related, meanings. In general, the term refers to a whole range of things. In everyday life, for example, a person might say that he or she is interested in the whole spectrum of news stories, meaning that he or she enjoys reading and hearing about anything to do with the news.

In the field of science, one meaning for the word spectrum has to do with the whole range of electromagnetic energies that exist. This range is known as the electromagnetic spectrum. All forms of electromagnetic energy travel through space in the form of waves that have distinctive wavelengths and frequencies. The wavelength of a wave is the distance between adjacent identical parts of the wave, as between two crests or two troughs (pronounced trawfs). The frequency of a wave is the number of crests (or troughs) that pass a given point in space per...