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Radio wave interference

Astronomers and astrophysicists collect signals from outer space using electromagnetic waves. A common problem for astrophysicists is the “pollution” from electromagnetic radiation pervading our surroundings from communication systems in general. Even everyday gadgets like our car keys having the facility to lock car doors remotely and being able to turn TVs on and off using remotes involve radio-wave frequencies. In order to prevent interference between all these electromagnetic signals, strict regulations are drawn up for different organizations to utilize different radio frequency bands.

One reason why we are sometimes asked to switch off our mobile phones (operating in the range of 1.9 GHz) on airplanes and in hospitals is that important communications or medical equipment often uses similar radio frequencies and their operation can be affected by frequencies used in the communication devices.

For example, radio waves used in magnetic resonance imaging (MRI) have frequencies on the order of 100 MHz, although this varies significantly depending on the strength of the magnetic field used and the nuclear type being scanned. MRI is an important medical imaging and research tool, producing highly detailed two- and three-dimensional images. Radio waves are broadcast, absorbed, and reemitted in a resonance process that is sensitive to the density of nuclei (usually protons or hydrogen nuclei).

The wavelength of 100-MHz radio waves is 3 m, yet using the sensitivity of the resonant frequency to the magnetic field strength, details smaller than a millimeter can be imaged. This is a good example of an exception to a rule of thumb (in this case, the rubric that details much smaller than the probe’s wavelength cannot be detected). The intensity of the radio waves used in MRI presents little or no hazard to human health.


Microwaves are the highest-frequency electromagnetic waves that can be produced by currents in macroscopic circuits and devices. Microwave frequencies range from about 10 9 Hz size 12{"10" rSup { size 8{9} } `"Hz"} {} to the highest practical LC size 12{ ital "LC"} {} resonance at nearly 10 12 Hz size 12{"10" rSup { size 8{"12"} } `"Hz"} {} . Since they have high frequencies, their wavelengths are short compared with those of other radio waves—hence the name “microwave.”

Microwaves can also be produced by atoms and molecules. They are, for example, a component of electromagnetic radiation generated by thermal agitation    . The thermal motion of atoms and molecules in any object at a temperature above absolute zero causes them to emit and absorb radiation.

Since it is possible to carry more information per unit time on high frequencies, microwaves are quite suitable for communications. Most satellite-transmitted information is carried on microwaves, as are land-based long-distance transmissions. A clear line of sight between transmitter and receiver is needed because of the short wavelengths involved.

Radar is a common application of microwaves that was first developed in World War II. By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds and aircraft. A Doppler shift in the radar echo can be used to determine the speed of a car or the intensity of a rainstorm. Sophisticated radar systems are used to map the Earth and other planets, with a resolution limited by wavelength. (See [link] .) The shorter the wavelength of any probe, the smaller the detail it is possible to observe.

Questions & Answers

what there factors affect the surface tension of a liquid
Promise Reply
formula for impedance
muyiwa Reply
ehat is central forces
Nita Reply
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Jonathan Reply
What does mean ohms law imply
Victoria Reply
ohms law state that the electricity passing through a metallic conductor is directly proportional to the potential difference across its end
what is matter
folajin Reply
Anything that occupies space
Any thing that has weight and occupies space
Anything which we can feel by any of our 5 sense organs
what is a sulphate
any answers
the time rate of increase in velocity is called
Blessing Reply
What is uniform velocity
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forces acting and lying on d same plane
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Peace Reply
How does a current follow?
Vineeta Reply
which one dc or ac current.
how does a current following?
AC current
AC current follows due to changing electric field and magnetic field.
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what is a semiconductor
Vineeta Reply
substances having lower forbidden gap between valence band and conduction band
what is a conductor?
replace lower by higher only
convert 56°c to kelvin
How does a current follow?
A semiconductor is any material whose conduction lies between that of a conductor and an insulator.
what is Atom? what is molecules? what is ions?
Abubakar Reply
atoms are the smallest unit of an element which is capable of behaving as a single unit
a molecule is d smallest unit of a substances capable of independent existence and can also retain the chemical proper ties of that substance
an ion is referred to as freely moving charged particles
What is a molecule
Samuel Reply
Is a unit of a compound that has two or more atoms either of the same or different atoms
A molecule is the smallest indivisible unit of a compound, Just like the atom is the smallest indivisible unit of an element.
what is a molecule?

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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