What is the Frequency of a Wave?
Radio waves, microwaves, X-rays, infrared light, all these names describe, in fact, the same phenomenon: The electromagnetic waves. An electromagnetic field surrounds us always, in the same way that air surrounds us. Electromagnetic waves are disturbances in the electromagnetic field, as the sound is a disturbance of air pressure. These disturbances or can be also said as waves – are moving at the speed of light, i.e., 299,792,458 meters/second
Electromagnetic waves, like any wave, are characterized by their wavelength and frequency. A specific form of the electromagnetic wave is visible light. There are many other types, but we do not call it “light,” even if it is. Each type of radiation has a frequency range. Presented here are all electromagnetic radiations, from those with the lowest frequencies: this is called the electromagnetic spectrum.
Which Electromagnetic wave has lowest Frequency?
The lowest frequencies are radio waves. On land, they are produced by antennas: the movement of electrons in the antennas produce these radio waves. Antennas on roofs are the opposite: waves produce electrons’ movements, i.e., the electric power in the receiving antenna. This current, which converts them into sound or picture, is amplified and sent to the radio or the television.
Microwaves have a frequency slightly higher. Microwave ovens use a very special frequency to heat food (in fact, it is a frequency that makes the water molecules vibrate, so it heats the molecules). Mobile phones tend to use close frequencies, causing some concern. But a phone has a thousand times smaller power than an oven, anyway.
A frequency a little higher, there is infrared. They are located, as their name suggests, just below the red in the frequency domain. They are mainly emitted by hot objects (like our bodies, for example).
Then there is the visible light: radiations of lower frequency are red. Those of the highest frequencies are blue and violet. You can manipulate this light through optical instruments: lenses, prisms, etc… The light is easy to manipulate because we can see it.
Beyond violet are ultraviolet, at higher frequencies. We do not see them, but you can feel their effects (sunburn…). It is also a black light.
Over again, the frequencies are important, which means that the light carries a lot of energy. So it can cause burns or damages. Also, an electromagnetic wave of high frequency is capable of crossing the matter. This can be useful, but it also means that if it does damages, they are internal. The ultraviolet rays are dangerous because they are not stopped by the upper layers of the skin, such as visible light.
They are still more energetic: X-rays, for example. They are dangerous at high doses but so useful! They pass through your body without any problems, but not completely. They cross bones less well – hence they are used in radiography.
Finally, the most energetic of all are gamma rays. It’s also light, but so much energy that they are very dangerous can cause serious damage to living beings. However, and it can be a problem, nothing stops them, or almost: they can cross a safe! Nuclear reactions primarily produce them.
Recommended Books:
Field and Wave Electromagnetics
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