So what are frequencies? Frequency refers to the number of cycles per second occur in an electromagnetic transmission. According to our current understanding of the universe, all energy in the universe travels in electromagnetic waves. James Clerk Maxwell was able to demonstrate that a changing magnetic field will induce a changing electric field, which is how energy travels. Heinrich Hertz produced radio waves using this theory. The unit used to measure electromagnetic transmissions is the hertz, with one hertz being equal to one cycle per second.

Engineers talk about the hertz of radio frequencies (AM and FM), television frequencies, microwave frequencies, satellite frequencies, and even light frequencies (as colors) when they speak about data link layerRadio, Television, WiMax, WiFi, Bluetooth and fiber optic communications.

Using the analogy of a human holding one end of a string tied to a doorknob 1 meter away, the faster the human shakes his hand up and down on the string, the more waves he creates in the string (to a limit).  Shake your hand twice a second, and that's two waves per second, or 2 hertz. The high points of the moving string are the maximums, and the lowest points are the minimums. The distance between one minimum and the next maximum is one cycle, or one 'wave'. The distance between the minimum of the first wave, and the minimum of the next wave is called the 'period'. The term Frequency is used to refer to how many waves are created per second. The more waves occur in one second, the higher the frequency, the fewer the number of waves (cycles) the lower the frequency.

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