Electromagnetic Spectrum: Radio Waves

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.

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MEASURING THE ELECTROMAGNETIC SPECTRUM

The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group. Radiation is energy that travels and spreads out as it goes - visible light that comes from a lamp in your house and radio waves that come from a radio station are two types of electromagnetic radiation.

Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays.

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RADIO WAVES

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Like all other electromagnetic waves, they travel at the speed of light. Naturally-occurring radio waves are made by lightning, or by astronomical objects. Artificially-generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, satellite communication, computer networks and innumerable other applications.

Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves may cover a part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel around the world, and much shorter wavelengths bend or reflect very little and travel on a line of sight.

Discovery and utilization: Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations, that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed, making practical the use of radio waves to transfer information through space.

Propagation: The study of electromagnetic phenomena such as reflection, refraction, polarization, diffraction and absorption is of critical importance in the study of how radio waves move in free space and over the surface of the Earth. Different frequencies experience different combinations of these phenomena in the Earth's atmosphere, making certain radio bands more useful for specific purposes than others.

Radio communication: In order to receive radio signals, for instance from AM/FM radio stations, a radio antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range). This is typically done via a resonator (in its simplest form, a circuit with a capacitor and an inductor). The resonator is configured to resonate at a particular frequency (or frequency band), thus amplifying sine waves at that radio frequency, while ignoring other sine waves. Usually, either the inductor or the capacitor of the resonator is adjustable, allowing the user to change the frequency at which it resonates.

In medicine: Radio frequency (RF) energy has been used in medical treatments for over 75 years generally for minimally invasive surgeries and coagulation, including the treatment of sleep apnea.

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[Bobbiethejean]

I don't understand how people can ~not~ find this fascinating. <3<3<3<3<3

[lostbuffalo]

@kurentmalik Another thing not widely known about Tesla is that he invented the transistor, the diode, the field effect transistor and on and on. Study his work in vacuum tubes. These components are developments of Tesla's vacuum tubes by simply replacing the vacuum in the tube with a semi permeable layer of silicon between the cathodes gates and anodes. the architecture and function of ic components is identical to Tesla's vacuum tube patents right down to the rare earth elements used.

[LynnColorado]

What a lucky group of human beings we are to be able to learn and share this kind of information. Thank you!

[chrisofnottingham]

@EclecticSceptic It isn't so much that a radio wave is stopped by things, its that the wave becomes more and more spread out until any one part of it is too small to detect. Its like a ripple on a pond. Even if the pond were a frictionless fluid, one wave is spread out over the circumference of an ever increasing circle but it still only contains the original energy, thus it gets forever smaller until it is no bigger than other random noise.

[MrTerminalZ]

3:26 and 3:29 were the sound affects of the hover disk jump from Shadow the Hedgehog.

[ChrissyboyH]

If you were on the outa regions of our solar system with a pretty much standard FM radio.. you would just about still recieve transmisions from Earth, altho what you would generally hear would be a 'wooshing' sound due countless stations on the same frequencies. Further out, reception would fade behind static. However, if you have a radio telescope of infinite size (if there was such a thing) and if you could travel lightyears in space, then you could hear transmissions from many years ago.

[luckystrke]

Since you touched upon it, you should probably explain that radio waves used for transmission of radio stations, use the waves as a carrier for audio information. Thats why you may lock on to just one frequency of radio waves, but still receive the whole audible spectrum.

[XorLavir]

I also want to mention Alexander Stepanovich Popov
en. wikipedia. org/ wiki/ Alexander_Stepanovich_Popov
was the first who demonstrated the PRACTICAL application of electromagnetic (radio) waves, although he did not apply for a patent for his invention.
In 1894 he built his first radio receiver.
Guglielmo Marconi was a rich businessman, who managed to create business from it, monopolizing invention.
That's why 100 hundred years of radio was celebrated in 1895 and not in 1896.

[eleminatus]

@Inwarwetrustful its not a sonar system. We dont send radio waves to planets and back. Its planets (or rather objects of space) that emit radio waves and we detect them!

[DJfractalflight]

3:44 Saturn really having trouble hocking out a loogie there at the end. Third time’s the charm!

[zarkoff]

@AnnaLang17

You didn't understand my question. Is the ~30 million km wavelength useful in radio astronomy. Seeing as it required using the Earth's magnetic field that would imply that the Earth's field could be used as a radio telescope, but to what degree.

[AnnaLang]

@zarkoff45 Yes, we can. Didn't you watch the video? Radio waves can be longer than Earth's diameter, which is around 8000 miles.
As far as I know, the longest radio wave detected is 30.5 million km or 18.9 million miles. But like julshz said there's no upper limit.

[lostbuffalo]

@kurentmalik Because they are talking about electromagnetic waves. Tesla called them Ether waves... same thing different nomenclature so if you don;t mention Tesla, you don't have to talk about ether. The word Ether to contemporary scientists is like the word spirit. its a word from a stupider time (in their estimate) and they think if they say ether they will lose credit. To avoid this they just avoid speaking of Tesla.

[emiliopersichilli]

Great storytelling, great video. Thank you

[Mr.Robert]

Watching this today in 2004. Understanding that NASA is sending a signal to Voyager 1 just now leaving our solar system. At that speed it's going to take 45 minutes round trip for the instructions to reach Voyager and make it back to NASA.
300, 000, 000 Meters Per Second.

[flexairz]

Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.

Basically this means that it will be very difficult to hear our transmissions.

[AnnaLang]

@zarkoff45 We can't use the field AS a telescope but it can induce an alternating current and voltage for some. The wavelength is important, but the size of the telescope and the efficiency of the receiver for amplifying signals is as equally important. Cosmic RW can be very weak, so it's hard to analyze and capture them from ground-based telescopes especially if they have longer wavelenghts. But if we do, we can use and study their composition, velocity etc and learn about their destination.

[DVampire]

I really enjoy this channel. Theres so much cool info to watch.

[kingsmithgaming]

So they are like really quite sounds that antennas are able to pick up on and make them loud enough for us to hear?

[nickoloes]

Nikola Tesla need sto be given more credit for the radio. Great man.