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Physics in Action Electromagnetic Spectrum S32LS0619:26

Physics in Action Electromagnetic Spectrum S32LS06

Physics in Action, The Electromagnetic Spectrum.


X-ray fine art photography of needlefish by Peter Dazeley. Attribution: Dazeley at English Wikipedia.

Orange LED emitting

Orange light-emitting diode. Attribution: Eeppeliteloop at English Wikipedia.

File:Spectre Terahertz.svg
Radar RAF Fylingdales

The new truncated pyramid Solid State Phased Array Radar (SSPAR) unit.


The electromagnetic spectrum is a collective term; referring to the entire range and scope of frequencies of electromagnetic radiation and their respective, associated photon wavelengths. It is the range of all the possible frequencies of known electromagnetic radiation (EM radiation or EMR), which is ultimately a form of radiant energy released by certain electromagnetic processes. Light, microwaves, X-rays, gamma- rays, T-rays, television emergency beacon signals, satellite communications, radar and radio waves are all part of it.

The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation at the short-wavelength (high-frequency) end, thereby covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. Visible light lies toward the shorter end, with wavelengths from 400 to 700 nanometres. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length. Until the middle of the 20th century it was believed by most physicists that this spectrum was infinite and continuous.

Nearly all types of electromagnetic radiation can be used for spectroscopy, to study and characterize matter. Other technological uses are described under electromagnetic radiation.

The electromagnetic spectrum as a tableEdit

Class   Freq-
Ionizing radiation|Ionizing
γ Gamma rays   300 Exahertz|EHz 1 Picometre|pm 1.24 Mega-|MeV
  30 EHz 10 pm 124 Kilo-|keV
HX Hard X-rays  
  3 EHz 100 pm 12.4 keV
SX Soft X-rays  
  300 Petahertz|PHz 1 Nanometre|nm 1.24 keV
  30 PHz 10 nm 124 electronvolt|eV
EUV Extreme ultraviolet|Extreme
  3 PHz 100 nm 12.4 eV
  NUV Near ultraviolet|Near
Visible light|Visible   300 Terahertz (unit)|THz 1 Micrometre|μm 1.24 eV
NIR Near infrared  
    30 THz 10 μm 124 Milli-|meV
MIR Mid infrared  
  3 THz 100 μm 12.4 meV
FIR Far infrared  
  300 Gigahertz|GHz 1 Millimetre|mm 1.24 meV


Radio wave|radio
EHF Extremely high frequency|Extremely high
  30 GHz 1 Centimetre|cm 124 micro-|μeV
SHF Super high frequency|Super high
  3 GHz 1 Decimetre|dm 12.4 μeV
UHF Ultra high frequency|Ultra high
  300 Megahertz|MHz 1 Metre|m 1.24 μeV
VHF Very high frequency|Very high
  30 MHz 10 m 124 nano-|neV
HF High frequency|High
  3 MHz 100 m 12.4 neV
MF Medium frequency|Medium
  300 kilohertz|kHz 1 Kilometre|km 1.24 neV
LF Low frequency|Low
  30 kHz 10 km 124 Pico-|peV
VLF Very low frequency|Very low
  3 kHz 100 km 12.4 peV
  ULF Ultra low frequency  
  300 hertz|Hz 1 Megametre|Mm 1.24 peV
SLF Super low frequency|Super low
  30 Hz 10 Mm 124 femto-|feV
ELF Extremely low frequency|Extremely low
  3 Hz 100 Mm 12.4 feV

Ultraviolet light tableEdit

Name Abbreviation Wavelength(nm) Photon energy(eV, aJ) Notes / alternative names
Ultraviolet A UVA 315–400 3.10–3.94, 0.497–0.631 Long-wave, black light, not absorbed by the ozone layer
Ultraviolet B UVB 280–315 3.94–4.43, 0.631–0.710 Medium-wave, mostly absorbed by the ozone layer
Ultraviolet C UVC 100–280 4.43–12.4, 0.710–1.987 Short-wave, germicidal, completely absorbed by the ozone layer and atmosphere
Near ultraviolet NUV 300–400 3.10–4.13, 0.497–0.662 Visible to birds, insects and fish
Middle ultraviolet MUV 200–300 4.13–6.20, 0.662–0.993
Far ultraviolet FUV 122–200 6.20–12.4, 0.993–1.987
Hydrogen Lyman-alpha H Lyman-α 121–122 10.16–10.25, 1.628–1.642 Spectral line at 121.6 nm, 10.20 eV. Ionizing radiation at shorter wavelengths
Vacuum ultraviolet VUV 10–200 6.20–124, 0.993–19.867 Strongly absorbed by atmospheric oxygen, though 150–200 nm wavelengths can propagate through nitrogen
Extreme ultraviolet EUV 10–121 10.25–124, 1.642–19.867 Entirely ionizing radiation by some definitions; completely absorbed by the atmosphere

Visible lightwave tableEdit

Color Wavelength Frequency Photon energy
Purple (Ultra near ultraviolet can be seen by a few people, plus most birds, insects and fish to who see UV to a  much greater degree than people.) ~380 nm ~668THz ~2.75 eV
violet 380–450 nm 668–789 THz 2.75–3.26 eV
blue 450–495 nm 606–668 THz 2.50–2.75 eV
green 495–570 nm 526–606 THz 2.17–2.50 eV
yellow 570–590 nm 508–526 THz 2.10–2.17 eV
orange 590–620 nm 484–508 THz 2.00–2.10 eV
red 620–750 nm 400–484 THz 1.65–2.00 eV
Crimson (Ultra near infrared can be seen by a few people, plus a few birds, insects and bats to who see IR to a slightly greater degree than people.) ~750 nm ~484 THz ~2.00 eV

Infrared light tableEdit

Division Name Abbreviation Wavelength Frequency Photon Energy Temperature† Characteristics
Near-infrared NIR, IR-A DIN 0.75–1.4 µm 214–400 THz 886–1653 meV 3,864–2,070 K

(3,591–1,797 °C)

Defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night visiondevices such as night vision goggles.
Short-wavelength infrared SWIR, IR-B DIN 1.4–3 µm 100–214 THz 413–886 meV 2,070–966 K

(1,797–693 °C)

Water absorption increases significantly at 1450 nm. The 1530 to 1560 nm range is the dominant spectral region for long-distance telecommunications.
Mid-wavelength infrared MWIR, IR-C DIN; MidIR.[12] Also called intermediate infrared (IIR) 3–8 µm 37–100 THz 155–413 meV 966–362 K

(693–89 °C)

In guided missile technology the 3–5 µm portion of this band is the atmospheric window in which the homing heads of passive IR 'heat seeking' missiles are designed to work, homing on to the Infrared signature of the target aircraft, typically the jet engine exhaust plume. This region is also known as thermal infrared.
Long-wavelength infrared LWIR, IR-C DIN 8–15 µm 20–37 THz 83–155 meV 362–193 K

(89 – −80 °C)

The "thermal imaging" region, in which sensors can obtain a completely passive image of objects only slightly higher in temperature than room temperature - for example, the human body - based on thermal emissions only and requiring no illumination such as the sun, moon, or infrared illuminator. This region is also called the "thermal infrared".
Far-infrared FIR 15–1000 µm 0.3–20 THz 1.2–83 meV 193–3 K

(−80.15 – −270.15 °C)

(see also far-infrared laser and far infrared)

Radiowave tableEdit

Band name. Abbreviation. ITU band. Frequency

and wavelength in air.

Example uses.
Tremendously low frequency TLF < 3 Hz

> 100,000 km

Natural and artificial electromagnetic noise and brain waves (1Hz).
Extremely low frequency ELF 3–30 Hz

100,000 km – 10,000 km

Communication with submarines
Super low frequency SLF 30–300 Hz

10,000 km – 1000 km

Communication with submarines
Ultra low frequency ULF 300–3000 Hz

1000 km – 100 km

Submarine communication, communication within mines
Very low frequency VLF 4 3–30 kHz

100 km – 10 km

Navigationtime signals, submarine communication, wireless heart rate monitorsgeophysics
Low frequency LF 5 30–300 kHz

10 km – 1 km

Navigation, clock time signals, AM longwave broadcasting (Europe and parts of Asia), RFID,amateur radio
Medium frequency MF 6 300–3000 kHz

1 km – 100 m

AM (medium-wave) broadcasts, amateur radio, avalanche beacons
High frequency HF 7 3–30 MHz

100 m – 10 m

Shortwave broadcasts, citizens' band radio, amateur radio and over-the-horizon aviation communications, RFIDover-the-horizon radarautomatic link establishment (ALE) / near-vertical incidence skywave (NVIS) radio communications, marine and mobile radio telephony
Very high frequency VHF 8 30–300 MHz

10 m – 1 m

FMtelevision broadcasts and line-of-sight ground-to-aircraft and aircraft-to-aircraft communications, land mobile and maritime mobile communications, amateur radio, weather radio
Ultra high frequency UHF 9 300–3000 MHz

1 m – 100 mm

Television broadcasts, microwave ovenmicrowave devices/communications, radio astronomy,mobile phoneswireless LANBluetoothZigBeeGPS and two-way radios such as land mobile,FRS and GMRS radios, amateur radio
Super high frequency SHF 10 3–30 GHz

100 mm – 10 mm

Radio astronomy, microwave devices/communications, wireless LAN, most modern radars,communications satellites, satellite television broadcasting, DBS, amateur radio
Extremely high frequency EHF 11 30–300 GHz

10 mm – 1 mm

Radio astronomy, high-frequency microwave radio relay, microwave remote sensing, amateur radio, directed-energy weaponmillimeter wave scanner
Terahertz orTremendously high frequency THz or THF 12 300–3,000 GHz

1 mm – 100 μm

Terahertz imaging – a potential replacement for X-rays in some medical applications, ultrafast molecular dynamics, condensed-matter physicsterahertz time-domain spectroscopy, terahertz computing/communications, sub-mm remote sensing, amateur radio

Radio and Microwave sub-frequenciesEdit

Lualualei VLF transmitter-001:28

Lualualei VLF transmitter-0

lualualei vlf transmitter wiki lualualei vlf transmitter vlf transmitter lualualei very low frequency lualualei vlf transmitter.

Extremely low frequency Edit

Clam Lake ELF

A 1982 aerial view of the U.S. Navy Clam Lake, Wisconsin ELF transmitter facility, used to communicate with deeply submerged submarines.

  • Frequency range- 3 to 30 Hz.
  • Wavelength range- 100,000 to 10,000 km, respectively.

Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.

ELF radio waves are generated by lightning and natural disturbances in Earth's magnetic field, so they are a subject of research by atmospheric scientists. Because of the difficulty of building antennas that can radiate such long waves, ELF frequencies have been used in only a very few human-made communication systems. ELF waves can penetrate seawater, which makes them useful in communication with submarines. The US, Russia, and India are the only nations known to have constructed ELF communication facilities. The U.S. facilities were used between 1985 and 2004 but are now decommissioned. ELF waves can also penetrate significant distances into earth or rock, and "through-the-earth" underground mine communication systems use frequencies of 300 to 3000 Hz. The frequency of alternating current flowing in electric power grids, 50 or 60 Hz, also falls within the ELF band, making power grids an unintentional source of ELF radiation.

Super low frequencyEdit

  • Frequency range- 30 to 300 Hz
  • Wavelength range- 10,000 to 1,000 km

Super low frequency (SLF) is electromagnetic waves (radio waves) in the frequency range between 30 hertz and 300 hertz. They have corresponding wavelengths of 10,000 to 1,000 kilometers. This frequency range includes the frequencies of AC power grids (50 hertz and 60 hertz). Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz.

Because of the extreme difficulty of building transmitters that can generate such long waves, frequencies in this range have been used in very few artificial communication systems. However, SLF waves can penetrate seawater to a depth of hundreds of meters. Therefore, in recent decades the U.S., Russian and Indian military have built huge radio transmitters using SLF frequencies to communicate with their submarines. The U.S. naval service is called Seafarer and operates at 76 hertz. It became operational in 1989 but was discontinued in 2004 due to advances in VLF communication systems. The Russian service is called ZEVS and operates at 82 hertz. The Indian Navy has an operational ELF communication facility at the INS Kattabomman naval base to communicate with its Arihant class and Akula class submarines. 

The requirements for receivers at SLF frequencies is less stringent than transmitters, because the signal strength (set by atmospheric noise) is far above the noise floor of the receiver, so small, inefficient antennas can be used. Radio amateurs have received signals in this range using simple receivers built around personal computers, with coil or loop antennas connected to the PCs sound card. Signals are analysed by a software fast Fourier transform algorithm and converted into audible sound. 

Ultra low frequencyEdit

  • Frequency range- 0.3 to 3 kHz
  • Wavelength range- 1,000 to 100 km

Ultra low frequency (ULF) is the ITU designation for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz. In magnetosphere science and seismology, alternative definitions are usually given, including ranges from 1 mHz to 100 Hz, 1 mHz to 1 Hz, 10 mHz to 10 Hz. Frequencies above 3 Hz in atmosphere science are usually assigned to the ELF range.

Many types of waves in the ULF frequency band can be observed in the magnetosphere and on the ground. These waves represent important physical processes in the near-Earth plasma environment. The speed of the ULF waves is often associated with the Alfvén velocity that depends on the ambient magnetic field and plasma mass density.

This band is used for communications in mines, as it can penetrate the earth.

Very low frequencyEdit

  • Frequency range- 3 to 30 kHz
  • Wavelength range- 100 to 10 km

Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3 kHz to 30 kHz and corresponding wavelengths from 100 to 10 kilometres, respectively. The band is also known as the myriametre band or myriametre wave as the wavelengths range from one to ten myriametres (an obsolete metric unit equal to 10 kilometres). Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and for secure military communication. Since VLF waves can penetrate at least 40 meters (120 ft) into saltwater, they are used for military communication with submarines.

Low frequencyEdit

File:Atomic clock.jpg
  • Frequency range- 30 to 300 kHz.
  • Wavelength range- 10 to 1 km.

Low frequency (low freq) or LF is the ITU designation for radio frequencies (RF) in the range of 30 kHz–300 kHz. As its wavelengths range from ten kilometres to one kilometre, respectively, it is also known as the kilometre band or kilometre wave.

LF radio waves exhibit low signal attenuation, making them suitable for long-distance communications. In Europe and areas of Northern Africa and Asia, part of the LF spectrum is used for AM broadcasting as the "longwave" band. In the western hemisphere, its main use is for aircraft beacon, navigation (LORAN), information, and weather systems. A number of time signal broadcasts are also broadcast in this band.

Medium frequencyEdit

File:2008-07-28 Mast radiator.jpg
  • Frequency range- 0.3 to 3 MHz.
  • Wavelength range- 1000 to 100 m.

Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kHz to 3 MHz. Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten to one hectometer (1,000 to 100 m). Frequencies immediately below MF are denoted low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.

High frequencyEdit

File:ICOM IC-M700PRO.jpg
  • Frequency range- 3 to 30 MHz.
  • Wavelength range- 100 to 10 m.

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 MHz. It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred metres). Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances. The band is used by international shortwave broadcasting stations (2.31–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

Very high frequencyEdit

  • Frequency range- 30 MHz to 300 MHz.
  • Wavelength range- 10 to 1 m.

Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 MHz to 300 MHz, with corresponding wavelengths of ten to one meters. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

Common uses for VHF are FM radio broadcasting, television broadcasting, two way land mobile radio systems (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur radio, and marine communications. Air traffic control communications and air navigation systems (e.g. VOR & ILS) work at distances of 100 kilometres or more to aircraft at cruising altitude.

VHF was used for analog television stations in the US, and continues to be used for digital television as well as in Europe but in the latter only Band III is used even though originally Band I was planned to be used. Some older DVB-T receivers included channels E2 to E4 but newer ones only go down to channel E5.

Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 MHz to 300 MHz, with corresponding wavelengths of ten to one meters. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

Common uses for VHF are FM radio broadcasting, television broadcasting, two way land mobile radio systems (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur radio, and marine communications. Air traffic control communications and air navigation systems (e.g. VOR & ILS) work at distances of 100 kilometres or more to aircraft at cruising altitude.

VHF was used for analog television stations in the US, and continues to be used for digital television as well as in Europe but in the latter only Band III is used even though originally Band I was planned to be used. Some older DVB-T receivers included channels E2 to E4 but newer ones only go down to channel E5.

Ultra high frequencyEdit

File:UHF TV Antenna 001.JPG
File:Reflective array, bow tie, grid, or panel UHF television antenna,.jpg
File:Binatone MR 200 radio 1.jpg
  • Frequency range- 300 MHz to 3 GHz.
  • Wavelength range- 1 m to 1 dm.

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 MHz and 3 GHz, also known as the decimetre band as the wavelengths range from one meter to one decimeter. Radio waves with frequencies above the UHF band fall into the SHF (super-high frequency) or microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, and numerous other applications.

The IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2 GHz and the S band between 2 and 4 GHz.

Super high frequencyEdit

File:Parabolic antennas.JPG
Radar antennas on USS Theodore Roosevelt SPS-64

A X-band (8 - 12 GHz) marine radar antenna on a ship. The rotating bar sweeps a vertical fan-shaped beam of microwaves around the water surface to the horizon, detecting nearby ships and other obstructions

  • Frequency range- 3 to 30 GHz.
  • Wavelength range- 1 dm to 1 cm.

Super high frequency (SHF) is the ITU designation for radio frequencies (RF) in the range between 3 GHz and 30 GHz. This band of frequencies is also known as the centimetre band or centimetre wave as the wavelengths range from one to ten centimetres. These frequencies fall within the microwave band, so radio waves with these frequencies are called microwaves. The small wavelength of microwaves allows them to be directed in narrow beams by aperture antennas such as parabolic dishes, so they are used for point-to-point communication and data links and for radar. This frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave radio relay links, and numerous short range terrestrial data links. Wireless USB technology is anticipated to use approximately one-third of this spectrum.[citation needed]

Frequencies in the SHF range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.

Extremely high frequency Edit

File:The Atacama Compact Array.jpg
File:CableFree MMW Link installed in UAE.jpg
File:Minsk port bow AK-630 CIWS gun fire control radar.JPG
  • Frequency range- 30 to 300 GHz.
  • Wavelength range- 1 cm to 1 mm.

Extremely high frequency (EHF) is the International Telecommunications Union (ITU) designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz. It lies between the super high frequency band, and the far infrared band which is also referred to as the terahertz gap. Radio waves in this band have wavelengths from ten to one millimetre, giving it the name millimetre band or millimetre wave, sometimes abbreviated MMW or mmW. Millimetre-length electromagnetic waves were first investigated in the 1890s by Indian scientist Jagadish Chandra Bose.

Compared to lower bands, radio waves in this band have high atmospheric attenuation; they are absorbed by the gases in the atmosphere. Therefore, they have a short range and can only be used for terrestrial communication over about a kilometer. Absorption by humidity in the atmosphere is significant except in desert environments, and attenuation by rain (rain fade) is a serious problem even over short distances. However the short propagation range allows smaller frequency reuse distances than lower frequencies. The short wavelength allows modest size antennas to have a small beam width, further increasing frequency reuse potential.

Traffic police use speed-detecting radar guns in the Ka-band (33.4 – 36.0 GHz).

Tremendously high frequencyEdit

File:Spectre Terahertz.svg
File:Processing of low resolution THz images.png
File:Optical, THz and X-ray Images.png
  • Frequency range- 300 GHz to 3 THz.
  • Wavelength range- 1 mm to 100 μm.

Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency, T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahertz (THz; 1 THz = 1012 Hz). Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm (or 100 μm). Because terahertz radiation begins at a wavelength of one millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy.

Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the terahertz gap, where technology for its generation and manipulation is in its infancy. It represents the region in the electromagnetic spectrum where the frequency of electromagnetic radiation becomes too high to be measured digitally via electronic counters, so must be measured by proxy using the properties of wavelength and energy. Similarly, the generation and modulation of coherent electromagnetic signals in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques. Photon energy in the THz regime is less than the band-gap energy of nonmetallic materials and thus THz radiation can penetrate such materials. THz beams transmitted through materials can be used for material characterization, layer inspection and as an alternative to X-rays for producing high resolution images of the interior of solid objects.

Comparable lengthsEdit

  1. Gamma rays 1 picometre.
  2. Far IR 15 micrometers (µm) to 1 mm.
  3. EHF 1 cm to 10 cm.
  4. VHF 10 m to 1 m.
  5. MF 1,000 m to 100 m.
  6. ULF 1,000 km to 100 km.
  7. SLF 10,000 km to 1,000 km.


  1. Equal to 1×10−12 m, or one trillionth (1/1,000,000,000,000) of a metre, which is the SI base unit of length. A helium atom has an estimated (calculated) diameter of 62 picometres.
  2. The smallest impairment devision on the standard metric UK plastic school ruler is 1 mm.
  3. Reading station, UK to Redding Signal-box, UK 110 m.
  4. Redding Signal-box to Boston Rd, Henley 9.3 km.
  5. Redding Signal-box to Boston Rd, Henley to Burton St, Cheltenham 91.7 km.
  6. Burton St, Cheltenham to Grant St, Woodlands, Glasgow 464.2 km.
  7. Grant St, Woodlands, Glasgow to Owaija Industrial Aria, Aleppo 3,792.2 km.
  8. Owaija Industrial Aria, Aleppo to Fire Department Unit, Tribhuvan International Airport, Kathmandu. 4,603.6 km.
  9. Fire Department Unit, Tribhuvan International Airport, Kathmandu to Hospital Regonal Comadoro Rividavia 16,890.5 km.
  10. Hospital Regonal Comadoro Rividavia, Argentina to Reading station, UK 12,522.6 Km.


Infrared radiation, (AKA: infrared or IR) is used in infrared spectroscopy, measuring devices, night-vision devices, infrared astronomy, thermal-infrared imaging, target acquisition, surveillance, night vision, weapons homing devices, target tracking devices, thermal efficiency analysis, environmental monitoring, industrial facility inspections, remote temperature sensing, short-ranged wireless communication, spectroscopy, and weather forecasting.


Ultraviolet (UV) is used in "Black lights", Short-wave ultraviolet lamps, .

Arial sizeEdit

The longer the wave length, the longer the aerial. TV aerials are thus smaller then navy aerials fore radioing subs. A civil radio aerial is between the two.

Modern SPOT satellite imaging usesEdit

The SPOT 6 and SPOT 7 satellites are phased in the same orbit as Pléiades 1A and Pléiades 1B at an altitude of 694 km, forming a constellation of 2-by-2 satellites - 90° apart from one another.

  • Image product resolution:
    • Panchromatic: 1.5 m.
    • Colour merge: 1.5 m.
    • Multi-spectral: 6 m.
  • Spectral bands, with simultaneous panchromatic and multi-spectral acquisitions:
    • Panchromatic (450 – 745 nm).
    • Blue (450 – 525 nm).
    • Green (530 – 590 nm).
    • Red (625 – 695 nm).
    • Near-infrared (760 – 890 nm).
  • Other image data.
    • Footprint: 60 km × 60 km.
    • Responsive satellite tasking, with six tasking plans per day, per satellite.
    • Capacity to acquire up to 3 million km2 daily.

LED light colours and types tableEdit

Color Wavelength [nm] Voltage drop [ΔV] Semiconductor material
Infrared λ > 760 Δ

V < 1.63

Gallium arsenide (GaAs)

Aluminium gallium arsenide (AlGaAs)

Red 610 < λ < 760 1.63 < ΔV < 2.03 Aluminium gallium arsenide (AlGaAs)

Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP)

Orange 590 < λ < 610 2.03 < ΔV < 2.10 Gallium arsenide phosphide (GaAsP)

Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP)

Yellow 570 < λ < 590 2.10 < ΔV < 2.18 Gallium arsenide phosphide (GaAsP)

Aluminium gallium indium phosphide (AlGaInP) Gallium(III) phosphide (GaP)

Green 500 < λ < 570 1.9[76] < ΔV < 4.0 Traditional green:

Gallium(III) phosphide (GaP) Aluminium gallium indium phosphide (AlGaInP) Aluminium gallium phosphide (AlGaP) Pure green: Indium gallium nitride (InGaN) / Gallium(III) nitride (GaN)

Blue 450 < λ < 500 2.48 < ΔV < 3.7 Zinc selenide (ZnSe)

Indium gallium nitride (InGaN) Silicon carbide (SiC) as substrate Silicon (Si) as substrate—under development

Violet 400 < λ < 450 2.76 < ΔV < 4.0 Indium gallium nitride (InGaN)
Ultraviolet λ < 400 3 < ΔV < 4.1 Indium gallium nitride (InGaN) (385-400 nm)

Diamond (235 nm)[77] Boron nitride (215 nm)[78][79] Aluminium nitride (AlN) (210 nm)[80] Aluminium gallium nitride (AlGaN) Aluminium gallium indium nitride (AlGaInN)—down to 210 nm[81]

Pink Multiple types ΔV ≈3.3[82] Blue with one or two phosphor layers,

yellow with red, orange or pink phosphor added afterwards,

white with pink plastic, or white phosphors with pink pigment or dye over top.[83]

Purple Multiple types 2.48 < ΔV < 3.7 Dual blue/red LEDs,

blue with red phosphor, or white with purple plastic

White Broad spectrum 2.8 < ΔV < 4.2 Cool / Pure White: Blue/UV diode with yellow phosphor

Warm White: Blue diode with orange phosphor

Relevant technical terminologyEdit

Haverfordwest VHF-Transmitter - - 310155

Haverfordwest VHF-Transmitter Another picture of this big mast but this being much closer. The tower in front is very small only 40 feet when the main mast is 500 feet. The mast is the main station VHF-FM Transmitter for this area when Preseli is the main TV-Transmitter. Attribution: David Neale.

  1. Frequency
  2. fe
  3. Ultra low frequency
  4. Super_low_frequency
  5. Very_low_frequency
  6. Radio_wave
  7. Nanometre
  8. X-ray
  9. Mm
  10. Hz
  11. Microwave
  12. ne
  13. eV
  14. Wave- length
  15. Low_frequency
  16. km
  17. μm
  18. infrared
  19. THz
  20. me
  21. Extremely_high_frequency
  22. GHz
  23. Far infrared
  24. Super_high_frequency
  25. Ultra_high_frequency
  26. Very_high_frequency
  27. μe
  28. dm
  29. mm
  30. cm
  31. High_frequency
  32. m
  33. Medium_frequency
  34. /Kilohertz
  35. Ionizing radiation
  36. MHz
  37. Pico-
  38. Energy
  39. Visible
  40. Extremely_low_frequency
  41. Near_ultraviolet
  42. EHz
  43. pm
  44. Me
  45. ke
  46. X-rays
  47. Gamma rays
  48. Extreme ultraviolet
  49. PHz

Also seeEdit

All About the Electromagnetic Spectrum06:26

All About the Electromagnetic Spectrum

All About the Electromagnetic Spectrum. How can you see the unseen through a thermal imaging camera?

  1. RAF Fylingdales
  2. The DEW Line
  3. Radar
  4. AN/FPS-108 Cobra Dane radar
  5. Thule Air Base, Greenland
  6. AEW&C
  7. Boeing RC-135 Cobra Ball
  8. Cold War radio jamming
  9. XTAR
  10. EMP
  11. TV
  12. Microwave ovens
  13. Electromagnetic Pulse (EMP)
  14. POMCUS sites
  15. Nuclear fallout
  16. Nukes
  17. Radome
  18. Blue Vixen Radar
  19. Ferranti Blue Fox Radar
  20. Westinghouse AN/APG-66 fire-control radar
  21. Telecommunications
  22. Radio
  23. Space Satellites

External linksEdit


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