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Frequency

Examples of these electromagnetic waves include the light from the sun and the waves received by your cell phone or radio.



All electromagnetic waves propagate at the same speed in air or in space. This speed (the speed of light) is roughly 671 million miles per hour (1 billion kilometers per hour). This is roughly a million times faster than the speed of sound (which is about 761 miles per hour at sea level). The speed of light will be denoted as c in the equations that follow. We like to use "SI" units in science (length measured in meters,time in seconds,mass in kilograms), so we will forever remember that 3 * 10^8 m/s

 A traveling electric field has an associated magnetic field with it, and the two make up an electromagnetic wave.

 The spatial variation is given in Figure 1, and the the temporal (time) variation is given in Figure 2.
A Sinusoidal Wave plotted as a function of position.

A Sinusoidal Wave plotted as a function of time.

                       
The frequency (written f ) is simply the number of complete cycles the wave completes (viewed as a function of time) in one second (two hundred cycles per second is written 200 Hz, or 200 "Hertz").

The speed that the waves travel is how fast the waves are oscillating in time (f ) multiplied by the size of the step the waves are taken per period (wavelength).

Basically, the frequency is just a measure of how fast the wave is oscillating. And since all EM waves travel at the same speed, the faster it oscillates the shorter the wavelength. And a longer wavelength implies a slower frequency.

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