ELECTROMAGNETIC SPECTRUM

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Electromagnetic spectrum


The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation frequencies.[1] The "electromagnetic spectrum" (usually just spectrum) of an object is the characteristic distribution of electromagnetic radiation from that particular object.
The electromagnetic spectrum extends from below the frequencies used for modern radio (at the long-wavelength end) through gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometres down to a fraction the size of an atom. It is thought that the short wavelength limit is in the vicinity of the Planck length, and the long wavelength limit is the size of the universe itself (see physical cosmology), although in principle the spectrum is infinite and continuous.






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Legend[2][3][4]
γ= Gamma rays
MIR= Mid infrared HF= High freq.

HX= Hard X-Rays
FIR= Far infrared MF= Medium freq.

SX= Soft X-Rays Radio waves
LF= Low freq.

EUV= Extreme ultraviolet
EHF= Extremely high freq.
VLF= Very low freq.

NUV= Near ultraviolet SHF= Super high freq.
VF/ULF= Voice freq.

Visible light
UHF= Ultra high freq.
SLF= Super low freq.

NIR= Near Infrared
VHF= Very high freq.
ELF= Extremely low freq.

Freq=Frequency






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Origin:-

The phenomena associated with electricity and magnetism was studied over most of the nineteenth century. But the knowledge that the two fields were interdependent began with the fantastic discovery by Hans Christian Orsted in the early 1820’s. He learnt that magnetism is ultimately caused by moving electric charges or current, when he observed a magnetic compass needle to react to a current flowing through a wire placed near it.
Later on the simultaneous though separate discoveries made by Michael Faraday and Joseph Henry concerning electromagnetic induction in the 1830’s led to the theory of James Clerk Maxwell, which united electricity, magnetism and optics into one grand theory of light explanation of electromagnetic waves.

Maxwell published his work Treastise on Electricity and Magnetism (1873), in which he showed that four fundamental mathematical equations described the entire known electric and magnetic phenomenon. The first equation is Gauss’s law for electricity, which states that positive and negative charges create magnetic fields; Gauss’s law for magnetism states that currents create magnetic field, which have associated north and south poles, but single poles (monopoles) do not exist; Ampere’s law states that time varying magnetic fields induce time varying electric fields; and faraday’s law of induction states that time varying electric fields create time varying magnetic fields. Additionally, Maxwell’s equation predicted the existence of combined, changing electric and magnetic fields in the form of waves that traveled with the speed of light i.e. electromagnetic waves. He speculated that accelerated charges ultimately create these electromagnetic waves, that they should exist over a wide range of frequencies and wavelengths, that they traveled at the speed of light in a vacuum, and that they exhibited all the optical properties of visible light, such as reflection, refraction and diffraction.

Heinrich Rudolf Hertz in 1887 verified Maxwell’s theory experimentally ten years after his death. Hertz built an induction coil device, which was essentially a step up transformer whose high output voltage caused, sparks to jump back and forth across an air gap between two metal plates. One wire, bent so that it too had an air gap between its ends, was placed near another wire. Hertz noticed sparks jumping across the ends of this wire at the same frequency as the induction coil’s sparks. He concluded that electromagnetic waves propagated through air from the coil to the bent wire. These waves proved to be radio waves of about 1 meter in wavelength. He demonstrated that the waves exhibited all the usual properties of light; namely, they reflected, focused on parabolic mirrors, and refracted through glass. He caused them to interfere, setting up a standing wave pattern that enabled him to calculate their speed to be the speed of light. Later experiments demonstrated that a wide range of electromagnetic wavelengths and frequencies exist and led to the technologies of radio, television, radar and myriad other technologies important

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Theory:-

Many natural phenomena exhibit wavelike behavior. Water waves, earthquake waves, and sound waves all require a medium or substance through which to propagate. These are examples of mechanical waves. Light can also be described as waves- waves of changing electric and magnetic fields that propagate outward from their sources. These electromagnetic waves however do not require a medium. They propagate at 3,000,000,00
meters per second through vacuum. Electromagnetic waves are transverse waves. In simpler terms, the changing electric and magnetic fields oscillate perpendicular to each other and to the direction of the propagating waves.

The best source of electromagnetic waves is accelerated waves. An accelerated charge is one that is increasing or decreasing its speed or changing its direction of motion or both. Let us imagine two charges at rest in the vicinity of each other. They are immersed in each others electric force field. If one charge suddenly begins to oscillate up and down, the second charge experiences the change in the field of the first charge after some very small finite time elapses. The oscillating charge was accelerated. The moving charge’s electric fields change, as do their magnetic fields. These changing electric and magnetic fields generate each other through Faraday’s law of induction and Ampere’s law. These changing fields dissociate from the oscillating charge and propagate out into space at the speed of light.

All periodic waves, whether they are electromagnetic or mechanical, are characterized by such properties as wave length, frequency, and speed. For electromagnetic waves, wavelength measures the distance between the successive pulses of electric or magnetic fields. A waves’ frequency represents how many wave pulses pass by a given point each second and is measured in cycles per second or waves per second and is measured in cycles per second or waves per second. One wave per second is called one Hertz. Electromagnetic waves travel at the speed of light in vacuum, but they travel more slowly when they pass through various media such as air, glass, and water. A relationship among frequency, wavelength and speed exists for electromagnetic waves; the product of frequency and wavelength equals the speed of light. Thus, wavelength and frequency are inversely related. The longer the frequency lower is the wavelength and vice versa.

An entire spectrum of electromagnetic waves exists, which ranges from very low frequency wavelength (power waves) to very high wavelength (gamma rays). All wavelengths are collectively referred to as electromagnetic wavelengths and not merely the narrow range of wavelengths and frequencies identified as visible light.

The wave nature of light describes many aspects of its behavior. Nevertheless, radiation
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also has its particle like characteristics. Rather than infinite or nearly infinite series of electromagnetic waves emanating from some accelerated charge, light also appears to come in particle –like bursts of energy. These individual bursts of energy or quanta are called photons. Each photon possesses an amount of energy that directly depends on the frequency of the associated electromagnetic wave. Doubling the frequency of the photon of radiation doubles its energy. Thus, all types of electromagnetic waves, photons of power waves possess the least energy and gamma-ray photons possess the greatest energy.

Since life on earth is bathed constantly in all forms of electromagnetic radiation, scientists must be aware of the potential risks, as well as benefits of exposures to electromagnetic waves.
Range of the spectrum
The spectrum covers EM wave energy having wavelengths from thousands of meters down to fractions of the size of an atom. Frequencies of 30 Hz and below can be produced by and are important in the study of certain stellar nebulae[5] and frequencies as high as 2.9 * 1027 Hz have been detected from astrophysical sources.[6]
Electromagnetic energy at a particular wavelength λ (in vacuum) has an associated frequency f and photon energy E. Thus, the electromagnetic spectrum may be expressed equally well in terms of any of these three quantities. They are related by the equations:
frequency x wavelength or and or
Where m/s (speed of light) and is Planck's constant, .
So, high-frequency electromagnetic waves have a short wavelength and high energy; low-frequency waves have a long wavelength and low energy.
Whenever light waves (and other electromagnetic waves) exist in a medium (matter), their wavelength is decreased. Wavelengths of electromagnetic radiation, no matter what medium they are traveling through, are usually quoted in terms of the vacuum wavelength , although this is not always explicitly stated.
Generally, EM radiation is classified by coiled wavelength into radio wave, microwave, infrared, the visible region we perceive as light, ultraviolet, X-rays and gamma rays.

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The behavior of EM radiation depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. When EM radiation interacts with single atoms and molecules, its behavior also depends on the amount of energy per quantum it carries. Electromagnetic radiation can be divided into octaves — as sound waves are.[7]
Spectroscopy can detect a much wider region of the EM spectrum than the visible range of 400 nm to 700 nm. A common laboratory spectroscope can detect wavelengths from 2 nm to 2500 nm. Detailed information about the physical properties of objects, gases, or even stars can be obtained from this type of device. It is widely used in astrophysics. For example, many hydrogen atoms emit a radio wave photon which has a wavelength of 21.12 cm.
Types of radiation


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While the classification scheme is generally accurate, in reality there is often some overlap between neighboring types of electromagnetic energy. For example, SLF radio waves at 60 Hz may be received and studied by astronomers, or may be ducted along wires as electric power. Also, some low-energy gamma rays actually have a longer wavelength than some high-energy X-rays. This is possible because "gamma ray" is the name given to the photons generated from nuclear decay or other nuclear and subnuclear processes, whereas X-rays on the other hand are generated by electronic transitions involving highly energetic inner electrons. Therefore the distinction between gamma ray and X-ray is related to the radiation source rather than the radiation wavelength.[8] Generally, nuclear transitions are much more energetic than electronic transitions, so usually, gamma-rays are more energetic than X-rays. However, there are a few low-energy nuclear transitions (e.g. the 14.4 keV nuclear transition of Fe-57) that produce gamma rays that are less energetic than some of the higher energy X-rays.
Radio frequency
Radio waves generally are utilized by antennas of appropriate size (according to the principle of resonance), with wavelengths ranging from hundreds of meters to about one millimeter. They are used for transmission of data, via modulation. Television, mobile phones, MRI, wireless networking and amateur radio all use radio waves.
Radio waves can be made to carry information by varying a combination of the amplitude, frequency and phase of the wave within a frequency band and the use of the radio spectrum is regulated by many governments through frequency allocation. When EM radiation impinges upon a conductor, it couples to the conductor, travels along it, and induces an electric current on the surface of that conductor by exciting the electrons of the conducting material. This effect (the skin effect) is used in antennas. EM radiation may also cause certain molecules to absorb energy and thus to heat up, thus causing thermal effects and sometimes burns; this is exploited in microwave ovens.




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Microwaves


Plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation.
The super high frequency (SHF) and extremely high frequency (EHF) of microwaves come next up the frequency scale. Microwaves are waves which are typically short enough to employ tubular metal waveguides of reasonable diameter. Microwave energy is produced with klystron and magnetron tubes, and with solid state diodes such as Gunn and IMPATT devices. Microwaves are absorbed by molecules that have a dipole moment in liquids. In a microwave oven, this effect is used to heat food. Low-intensity microwave radiation is used in Wi-Fi, although this is at intensity levels unable to cause thermal heating.
Volumetric heating, as used by microwaves, transfer energy through the material electro-magnetically, not as a thermal heat flux. The benefit of this is a more uniform heating and reduced heating time; microwaves can heat material in less than 1% of the time of conventional heating methods.
When active, the average microwave oven is powerful enough to cause interference at close range with poorly shielded electromagnetic fields such as those found in mobile medical devices and cheap consumer electronics.


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Terahertz radiation
Terahertz radiation is a region of the spectrum between far infrared and microwaves. Until recently, the range was rarely studied and few sources existed for microwave energy at the high end of the band (sub-millimetre waves or so-called terahertz waves), but applications such as imaging and communications are now appearing. Scientists are also looking to apply terahertz technology in the armed forces, where high frequency waves might be directed at enemy troops to incapacitate their electronic equipment.
Infrared radiation
The infrared part of the electromagnetic spectrum covers the range from roughly 300 GHz (1 mm) to 400 THz (750 nm). It can be divided into three parts:
• Far-infrared, from 300 GHz (1 mm) to 30 THz (10 μm). The lower part of this range may also be called microwaves. This radiation is typically absorbed by so-called rotational modes in gas-phase molecules, by molecular motions in liquids, and by phonons in solids. The water in the Earth's atmosphere absorbs so strongly in this range that it renders the atmosphere effectively opaque. However, there are certain wavelength ranges ("windows") within the opaque range which allow partial transmission, and can be used for astronomy. The wavelength range from approximately 200 μm up to a few mm is often referred to as "sub-millimetre" in astronomy, reserving far infrared for wavelengths below 200 μm.
• Mid-infrared, from 30 to 120 THz (10 to 2.5 μm). Hot objects (black-body radiators) can radiate strongly in this range. It is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions. This range is sometimes called the fingerprint region since the mid-infrared absorption spectrum of a compound is very specific for that compound.
• Near-infrared, from 120 to 400 THz (2,500 to 750 nm). Physical processes that are relevant for this range are similar to those for visible light.




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Visible radiation (light)


Visible Electromagnetic spectrum illustration.


The light spectrums of different grow lamps
Above infrared in frequency comes visible light. This is the range in which the sun and stars similar to it emit most of their radiation. It is probably not a coincidence that the human eye is sensitive to the wavelengths that the sun emits most strongly. Visible light (and near-infrared light) is typically absorbed and emitted by electrons in molecules and atoms that move from one energy level to another. The light we see with our eyes is really a very small portion of the electromagnetic spectrum. A rainbow shows the optical (visible) part of the electromagnetic spectrum; infrared (if you could see it) would be located just beyond the red side of the rainbow with ultraviolet appearing just beyond the violet end.
EM radiation with a wavelength between approximately 400 nm and 700 nm is detected by the human eye and perceived as visible light. Other wavelengths, especially near infrared (longer than 700 nm) and ultraviolet (shorter than 400 nm) are also sometimes referred to as light, especially when the visibility to humans is not relevant.
If radiation having a frequency in the visible region of the EM spectrum reflects off of an object, say, a bowl of fruit, and then strikes our eyes, this results in our visual perception of the scene. Our brain's visual system processes the multitude of reflected frequencies into different shades and hues, and through this not-entirely-understood psychophysical phenomenon, most people perceive a bowl of fruit.
At most wavelengths, however, the information carried by electromagnetic radiation is not directly detected by human senses. Natural sources produce EM radiation across the

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spectrum, and our technology can also manipulate a broad range of wavelengths. Optical fiber transmits light which, although not suitable for direct viewing, can carry data that can
be translated into sound or an image. The coding used in such data is similar to that used with radio waves.
Ultraviolet light


The amount of penetration of UV relative to altitude in Earth's ozone
Next in frequency comes ultraviolet (UV). This is radiation whose wavelength is shorter than the violet end of the visible spectrum.
Being very energetic, UV can break chemical bonds, making molecules unusually reactive or ionizing them, in general changing their mutual behavior. Sunburn, for example, is caused by the disruptive effects of UV radiation on skin cells, which can even cause skin cancer, if the radiation damages the complex DNA molecules in the cells (UV radiation is a proven mutagen). The Sun emits a large amount of UV radiation, which could quickly turn Earth into a barren desert; however, most of it is absorbed by the atmosphere's ozone layer before reaching the surface.
X-rays
After UV come X-rays. Hard X-rays have shorter wavelengths than soft X-rays. X-rays are used for seeing through some things and not others, as well as for high-energy physics and astronomy. Neutron stars and accretion disks around black holes emit X-rays, which enable us to study them.


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X-rays will pass through most substances, and this makes them useful in medicine and industry. X-rays are given off by stars, and strongly by some types of nebulae. An X-ray machine works by firing a beam of electrons at a "target". If the electrons are fired with enough energy, X-rays will be produced.

Gamma rays
After hard X-rays come gamma rays, which were discovered by Paul Ulrich Villard in 1900. These are the most energetic photons having no defined lower limit to their wavelength. They are useful to astronomers in the study of high energy objects or regions and find a use with physicists thanks to their penetrative ability and their production from radioisotopes. The wavelength of gamma rays can be measured with high accuracy by means of Compton scattering.
Note that there are no precisely defined boundaries between the bands of the electromagnetic spectrum. Radiation of some types have a mixture of the properties of those in two regions of the spectrum. For example, red light resembles infrared radiation in that it can resonate some chemical bonds.
Application of Electromagnetic Spectrum

All of these waves are electric and magnetic forces - forces which vary with time in direction and intensity. All have speed 186,000 miles per second = c = speed of light ! They move through vacuum,and do not need a ' carrier'. Speed decreases after entering materials
Light is a form of electromagnetic radiation. Other forms of electromagnetic radiation include radio waves, microwaves, infrared radiation, ultraviolet rays, X-rays, and gamma rays. All of these, known collectively as the electromagnetic spectrum, are fundamentally similar in that they move at 186,000 miles per second, (299,792 km/sec) the speed of light. The only difference between them is their wavelength, which is directly related to the amount of energy the waves carry. The shorter the wavelength of the radiation, the higher the energy.



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The rainbow of colors that we see in visible light represents only a very small portion of the electromagnetic spectrum. On one end of the spectrum are radio waves with wavelengths billions of times longer than those of visible light. On the other end of the spectrum are gamma rays. These have wavelengths millions of times smaller than those of visible light. The following are the basic categories of the electromagnetic spectrum, from longest to shortest wavelength:

Radio waves are used to transmit radio and television signals. Radio waves

have wavelengths that range from less than a centimeter to tens or even hundreds of meters. FM radio waves are shorter than AM radio waves. For example, an FM radio station at 100 on the radio dial (100 megahertz) would have a wavelength of about three meters. An AM station at 750 on the dial (750 kilohertz) uses a wavelength of about 400 meters. Radio waves can also be used to create images. Radio waves with wavelengths of a few centimeters can be transmitted from a satellite or airplane antenna. The reflected waves can be used to form an image of the ground in complete darkness or through clouds.

Microwave wavelengths range from approximately one millimeter (the thickness of a pencil lead) to thirty centimeters (about twelve inches). In a microwave oven, the radio waves generated are tuned to frequencies that can be absorbed by the food. The food absorbs the energy and gets warmer. The dish holding the food doesn't absorb a significant amount of energy and stays much cooler. Microwaves are emitted from the Earth, from objects such as cars and planes, and from the atmosphere. These microwaves can be detected to give information, such as the temperature of the object that emitted the microwaves

Infrared is the region of the electromagnetic spectrum that extends from the visible region to about one millimeter (in wavelength). Infrared waves include thermal radiation. For example, burning charcoal may not give off light, but it does emit infrared radiation which is felt as heat. Infrared radiation can be measured using electronic detectors and has applications in medicine and in finding heat leaks from houses. Infrared images obtained by sensors in satellites and airplanes can yield important

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information on the health of crops and can help us see forest fires even when they are enveloped in an opaque curtain of smoke.

Visible light. The rainbow of colors we know as visible light is the portion of the electromagnetic spectrum with wavelengths between 400 and 700 billionths of a meter (400 to 700 nanometers). It is the part of the electromagnetic spectrum that we see, and coincides with the wavelength of greatest intensity of sunlight. Visible waves have great utility for the remote sensing of vegetation and for the identification of different objects by their visible colors.

Ultraviolet radiation has a range of wavelengths from 400 billionths of a meter to about 10 billionths of a meter. Sunlight contains ultraviolet waves

which can burn your skin. Most of these are blocked by ozone in the Earth's upper atmosphere. A small dose of ultraviolet radiation is beneficial to humans, but larger doses cause skin cancer and cataracts. Ultraviolet wavelengths are used extensively in astronomical observatories. Some remote sensing observations of the Earth are also concerned with the measurement of ozone.

X-rays are high energy waves which have great penetrating power and are used extensively in medical applications and in inspecting welds. X-ray images of our Sun can yield important clues to solar flares and other changes on our Sun that can affect space weather. The wavelength range is from about ten billionths of a meter to about 10 trillionths of a meter.

Gamma rays have wavelengths of less than about ten trillionths of a meter. They are more penetrating than X-rays. Gamma rays are generated by radioactive atoms and in nuclear explosions, and are used in many medical applications. Images of our universe taken in gamma rays have yielded important information on the life and death of stars, and other violent processes in the universe.

Cosmic Rays. Despite their name, cosmic rays are not a part of the electromagnetic spectrum. Instead of radiation, cosmic rays are high-energy charged particles that travel through space at nearly the speed of light. Their extremely high energies are comparable to those of gamma
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rays at the upper end of the electromagnetic spectrum. The highest-energy cosmic rays originate outside our galaxy and provide information on distant objects such as quasars. Cosmic rays are detected when they hit the upper atmosphere, creating showers of particles in their interaction with atoms. These secondary particles can then be detected by instruments on the ground.

The Electromagnetic Waves


RADIOWAVES AM frequency given by stations: 550 – 1600 kHz (= 1.6 MHz)
FM frequency given by stations: 88 – 108 MHz
AM = amplitude modulated , FM = frequency modulated

MICROWAVES CELLULAR PHONE WAVES: frequency – 880 MHz =0.88 GHz , 'cell ' is the area covered by the antenna of( receiving or sending) company - therefore 'hand-off'.
MICROWAVE OVEN – heat water ( in food ) ; 2.45 GHz = 2,450 MHz
RADAR: used ( in conjunction with the Doppler Effect ) in ‘speed traps’ by police, in missiles to find airplanes, tanks, etc.; used by airports to guide airplanes, most 1 – 100 GHz ( G = giga )
INFRARED Just below visible red, also called heat radiation . With special cameras used to find heat losses from houses; by army to detect heat radiation from engines, people.
VISIBLE LIGHT RED, YELLOW, GREEN, BLUE, VIOLET - no white or black !!! White is the sensation for our brain when primary colors ( red, blue and green) fall onto the retina at the same time . Black is the absence of any light .
ULTRAVIOLET ALPHA- UV is energetic enough to cuase chemical reaction BETA UV causes damage to cell structure (tanning) and can cause genetic damage to cell DNA => possible cancer .
X-RAYS SOFT - X rays = lower Fr – range; used for taking x-ray pictures.
HARD - X - rays = higher Fr –range; used in cancer treatments to kill cancer cells.
GAMMA RAYS Frequency range overlaps with hard X-rays. Gamma rays originate though in the nucleus of atoms, not by electron – jumps between energy levels as frequencies higher than infraded do .
COSMIC RAYS Very high frequency, comes from sun, outer space = universe to us.
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EM Spectrum and Analytical Spectroscopy

Radiation
Type Radiation Source FrequencyRange (Hz) Wavelength Range Type of Transitions
gamma rays 1020 - 1024 <10-12 m nuclear
X-rays 1017 - 1020 1nm - 1 pm inner electron
ultraviolet deuterium lamp 1015 - 1017 400 nm - 1 nm outer electron. Electronic transitions, vibrational fine structure
visible Tungsten lamp 4 - 7.5 x 1014 750 nm - 400 nm
near-infrared Tungsten, dye laser 1 x 1014 - 4 x 1014 2500 nm - 750 nm (2.5 um - 750 nm) outer electron molecular vibrations. Vibrational transitions, rotational fine structure
infrared nerst glower, globar, Xe,Ar, discharge lamp 1013 - 1014 250,000 - 2,500 nm (25um - 2.5 um) outer electron, molecular vibrations. Vibrational transitions, rotational fine structure
microwaves 3 x 1011 - 1013 250,000 - 1,000,000,000 nm (1 mm - 25 um) molecular rotations,electron spin flips*, Rotational transitions
radio waves <3 x 1011 >1 mm nuclear spin flips*
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The Bands of the Electromegnetic Spectrum

Band Wavelength Frequency
MF medium frequency 300-3000 kHz
HF high frequency 3-30 MHz
Radio
FM
ShortWave 20 cm - 20 m
2.5-3.5 m
20 cm - 2.5 m 15 MHz - 1.5 GHz
85-120 MHz
120 MHz - 1.5 GHz
Microwave 0.01-20 cm 1.5-3000 GHz
EHF extremely high frequency 30-300 GHz
Far Infrared 20,000-100,000 nm 3000-15000 GHz
Near Infrared 700-20,000 nm 15000-430,000 GHz
Visible
Red
Orange
Yellow
Green
Blue
Violet 400-700 nm
620-760 nm
570-620 nm
550-570 nm
470-550 nm
440-470 nm
380-440 nm 430,000-750,000 GHz
Ultraviolet 50-190-400 nm 1015 - 1017 Hz
Soft XRay 1-20 nm 1017 - 1020 Hz
Hard XRay 0.1-1 nm
Gamma ray 0.1 - 0.000001 nm Highest 1020 - 1024 Hz


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EM Specrtum used in Broadcasting and Wirelass
Some common frequency bands
AM radio 535 kilohertz to 1.7 megahertz
Short wave radio 5.9 megahertz to 26.1 megahertz
Citizens band (CB) radio 26.96 megahertz to 27.41 megahertz
Television stations, channels 2 through 6 54 to 88megahertz
FM radio 88 megahertz to 108 megahertz
Television stations, channels 7 through 13 174 to 220 megahertz

Some Wireless Technology Bands
Garage door openers, alarm systems Around 40 megahertz
Standard cordless phones 40 to 50 megahertz
Baby monitors 49 megahertz
Radio controlled airplains Around 72 megahertz
Radio controlled cars (different from above) Around 75 megahertz
Wildlife tracking collars 215 to 220 megahertz
MIR space station 145 to 437 megahertz
Cell phones 824 to 849 megahertz
New 900 MHz cordless phones Around 900 megahertz (obviously)z
Air traffic control radar 960 to 1,215 megahertz
Global Positioning System 1,227 and 1,575 megahertz
Deep space radio communications 2,290 megahertz to 2,300 megahertz






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Bibliography:-

www.en.wikipedia.org
www.fusioned.gat.com
www.answers.com