The electromagnetic spectrum is the range of all possible frequencies or wavelengths of electromagnetic energy that we can detect and measure. Because many different objects generate electromagnetic energy in various frequencies, our ability to detect and examine these frequencies helps us explore and understand these objects. Because we have the ability to artificially generate most of these frequencies, we can also use them to do work. Many of these frequencies are critical to the world of telecommunications. After all, it is electromagnetic energy we are using when we communicate using most wireless technologies. That includes your cordless telephone, cell phone, Wi-Fi-capable laptop, remote control for your television or DVD player, car radio, and a variety of other communication tools.
Technically, the longest wavelength possible is one the size of the universe, and the shortest is believed to be near the Planck length. Practically, however, we have relatively little practical use for frequencies below a few hertz, which are a few kilometers in length, or frequencies above approximately 10-100 exahertz, which are fractions of an angstrom in length. We have divided all of the frequencies between these two extremes and given the various ranges names.
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