An antenna capable of transmitting or receiving electromagnetic (EM) waves. Examples of these electromagnetic waves include light from the sun, and the waves received by your cell phone. Your eyes are receiving antennas that detect electromagnetic waves at a specific frequency. "You see colors (red, green, blue) in each wave. Red and blue are just different frequencies of waves that your eyes can detect.
All electromagnetic waves propagate in air or space at the same speed. This speed is approximately $671 million per hour (1 billion kilometers per hour). This speed is called the speed of light. This speed is about a million times faster than the speed of sound waves. The speed of light would be written in the equation for "C". We will measure the length of time in meters, in seconds, and in kilograms. Equations for the future we should remember.
Before defining frequency, we must define what electromagnetic waves are. This is an electric field that spreads away from some source (antenna, sun, a radio tower, whatever). Traveling in an electrical field has a magnetic field associated with it. These two fields form an electromagnetic wave.
The universe allows these waves to take any shape. But the most important shape is the sine wave. This is plotted in Figure 1. Electromagnetic waves vary with location and time. The spatial changes are shown in Figure 1. The changes in time are shown in Figure 2.
figure 1. Sine wave plotted as a function of position.
figure 2. Plot a sine wave as a function of time.
Waves are periodic. The wave repeats once every second in a "T" shape. Plotted as a function in space, the number of meters after wave repetition is given here:
This is called wavelength. Frequency (written "F") is simply the number of complete cycles a wave completes in one second (the two-hundred-year cycle is seen as a function of time written 200 Hz or 200 "hertz" per second). Mathematically, this is the formula written below.
How fast someone walks depends on their step size (wavelength) multiplied by their rate of steps (frequency). Wave travel is similar in speed. How fast a wave oscillates ("F") multiplied by the size of the steps the wave takes each period ( ) gives the speed. The following formula should be remembered:
To summarize, frequency is a measure of how fast a wave oscillates. All electromagnetic waves travel at the same speed. Therefore, if an electromagnetic wave oscillates faster than a wave, the faster wave must also have a shorter wavelength. Longer wavelength means lower frequency.
Post time: Dec-01-2023
