What is the purpose of electromagnetic spectrum?

Answer 1

The electromagnetic spectrum is simply a way to display the range of electromagnetic energies in a manner that some associations can be discovered. Electromagnetic (EM) energy is composed of two waves, one electrostatic and one electromagnetic, that propagate at right angles to one another. Since we are looking at waves, it is natural to consider that they have different periods (the time it takes for one cycle to occur). We can then extend our thinking to consider the length of the wave, and also the frequency (the number of cycles per second) of the energy. Finally, we can consider the energy that is being propagated in the wave.

If we spread out all the different frequencies on a chart or diagram with the lowest frequencies to the left and the highest frequencies to the right (as we usually do), we have a display of the electromagnetic spectrum. Radio waves will be on the left. They have the longest wavelength and the longest period, and also the lowest frequency. A lot of the spectrum is taken up by radio waves. Further to the right come microwaves, then the EM radiation a bit lower in frequency than visible light, which is the infrared region of the spectrum. The optical spectrum (visible light) is represented by the reds, Oranges, yellows, etc., that we who are fortunate to be sighted can know. Beyond the violet visible light is the ultraviolet region, and then soft (lower energy) X-rays, and then the hard X-rays. Finally we find the gamma rays at the upper end of the spectrum.

Looking at all of the diagram, which is a representation arranged to a useful purpose, we can discover a number of things about electromagnetic energy. The different spectra (radio, microwave, etc.) all have distinct characteristics that we can apply in daily life. Low frequency radio waves are used in submarine communication. (They penetrate water to a degree, and can actually travel in a curve around the world.) Microwaves make your cellular phone work, and they heat food in a microwave oven. We (most of us) are visual creatures, and visible light from the optical spectrum allows us to navigate our way about. At a medical clinic, hospital or dental office, an X-ray allows health professionals to quite easily see things that cannot be looked at well with other methods. There is a lot to learn, and a display of the electromagnetic spectrum opens a door to understanding this type of energy.