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ERT247: GEOMATIC ENGGINEERING Electromagnetic radiation. GROUP A2: WAN MOHD ALIF NUR SALWANA KER LEE SHIANG SITI AFIQAH HUZAIFAH INTAN LIANA. Definition of electromagnetic radiation. the process of formation of a free electromagnetic field. Electromagnetic =

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ert247 geomatic enggineering electromagnetic radiation

ERT247:GEOMATIC ENGGINEERINGElectromagnetic radiation








definition of electromagnetic radiation
Definition of electromagnetic radiation

the process of formation of a free electromagnetic field

  • Electromagnetic =
  • Radiation = used to design the free that is radiated electromagnetic field itself
  • So in physics electromagnetic radiation is regarded as the emission of electromagnetic waves by electric charge that are moving under acceleration (current)
  • Electromagnetic radiation is emitted in discrete units known as photons that travel at the speed of light as electromagnetic waves. Electromagnetic energy is classified by increasing energy or decreasing wavelength into radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma-rays (Figure 1).

Electromagnetic radiation (often abbreviated E-M radiation or EMR) is a form of energy exhibiting wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation.


Electromagnetic radiation is classified according to the frequency of its wave. In order of increasing frequency and decreasing wavelength, these are radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The eyes of various organisms sense a small and somewhat variable window of frequencies called the visible spectrum. The photon is the quantum of the electromagnetic interaction and the basic "unit" of light and all other forms of electromagnetic radiation and is also the force carrier for the electromagnetic force. EM radiation carries energy and momentum that may be imparted to matter with which it interacts.

theory of electromagnetic radiation
  • Shows the relative wavelengths of the electromagnetic waves of three different colors of light (blue, green and red) with a distance scale in micrometres along the x-axis.

The theory that prove electromagnetic radiation:

Classical radiation theory (Maxwell`s theory) the theory of electromagnetic radiation was developed by James Clerk Maxwell and published in 1865. He showed that the speed of propagation of electromagnetic radiation should be identical with that of light , about 186,000 mi (300,000 km) per


James Clerk Maxwell first formally postulated electromagnetic waves. These were subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.

  • According to Maxwell's equations, a time-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form a propagating electromagnetic wave.
  • A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
the propagation direction of a light wave
The propagation direction of a light wave

V = E X B


electromagnetic wave
Electromagnetic wave
  • Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized wave propagating from right to left. The electric field is in a vertical plane and the magnetic field in a horizontal plane.

The physics of electromagnetic radiation is electrodynamics. Electromagnetism is the physical phenomenon associated with the theory of electrodynamics. Electric and magnetic fields obey the properties of superposition. Thus, a field due to any particular particle or time-varying electric or magnetic field contributes to the fields present ing the same space due to other causes. Further, as they are vector fields, all magnetic and electric field vectors add together according to vector addition. For example, in optics two or more coherent lightwaves may interact and by constructive or destructive interference yield a resultant irradiance deviating from the sum of the component irradiances of the individual lightwaves.


Since light is an oscillation it is not affected by travelling through static electric or magnetic fields in a linear medium such as a vacuum. However in nonlinear media, such as some crystals, interactions can occur between light and static electric and magnetic fields — these interactions include the Faraday effect and the Kerr effect.

  • n refraction, a wave crossing from one medium to another of different density alters its speed and direction upon entering the new medium. The ratio of the refractive indices of the media determines the degree of refraction, and is summarized by Snell's law. Light disperses into a visible spectrum as light passes through a prism because of the wavelength dependent refractive index of the prism material (Dispersion

EM radiation exhibits both wave properties and particle properties at the same time (see wave-particle duality). Both wave and particle characteristics have been confirmed in a large number of experiments. Wave characteristics are more apparent when EM radiation is measured over relatively large timescales and over large distances while particle characteristics are more evident when measuring small timescales and distances. For example, when electromagnetic radiation is absorbed by matter, particle-like properties will be more obvious when the average number of photons in the cube of the relevant wavelength is much smaller than 1. Upon absorption of light, it is not too difficult to experimentally observe non-uniform deposition of energy. Strictly speaking, however, this alone is not evidence of "particulate" behavior of light, rather it reflects the quantum nature of matter


There are experiments in which the wave and particle natures of electromagnetic waves appear in the same experiment, such as the self-interference of a single photon.True single-photon experiments (in a quantum optical sense) can be done today in undergraduate-level labs.[2] When a single photon is sent through an interferometer, it passes through both paths, interfering with itself, as waves do, yet is detected by a photomultiplier or other sensitive detector only once.

particle model
Particle Model
  • Because energy of an EM interaction is quantized, EM waves are emitted and absorbed as discrete packets of energy, or quanta, called photons. Because photons are emitted and absorbed by charged particles, they act as transporters of energy, and are associated with waves with frequency proportional to the energy carried. The energy per photon can be related to the frequency via the Planck–Einstein equation:[4]
  • where E is the energy, h is Planck's constant, and f is frequency. The energy is commonly expressed in the unit of electronvolt (eV). This photon-energy expression is a particular case of the energy levels of the more general electromagnetic oscillator, whose average energy, which is used to obtain Planck's radiation law, can be shown to differ sharply from that predicted by the equipartition principle at low temperature, thereby establishes a failure of equipartition due to quantum effects at low temperature.

As a photon is absorbed by an atom, it excites the atom, elevating an electron to a higher energy level. If the energy is great enough, so that the electron jumps to a high enough energy level, it may escape the positive pull of the nucleus and be liberated from the atom in a process called photoionisation. Conversely, an electron that descends to a lower energy level in an atom emits a photon of light equal to the energy difference. Since the energy levels of electrons in atoms are discrete, each element emits and absorbs its own characteristic frequencies.


Together, these effects explain the emission and absorption spectra of light. The dark bands in the absorption spectrum are due to the atoms in the intervening medium absorbing different frequencies of the light. The composition of the medium through which the light travels determines the nature of the absorption spectrum. For instance, dark bands in the light emitted by a distant star are due to the atoms in the star's atmosphere. These bands correspond to the allowed energy levels in the atoms. A similar phenomenon occurs for emission. As the electrons descend to lower energy levels, a spectrum is emitted that represents the jumps between the energy levels of the electrons. This is manifested in the emission spectrum of nebulae. Today, scientists use this phenomenon to observe what elements a certain star is composed of. It is also used in the determination of the distance of a star, using the red shift.



  • Any electric charge which accelerates, or any changing magnetic field, produces electromagnetic radiation. Electromagnetic information about the charge travels at the speed of light. Accurate treatment thus incorporates a concept known as retarded time (as opposed to advanced time, which is not physically possible in light ofcausality), which adds to the expressions for the electrodynamicelectric field and magnetic field. These extra terms are responsible for electromagnetic radiation. When any wire (or other conducting object such as an antenna) conducts alternating current, electromagnetic radiation is propagated at the same frequency as the electric current. At the quantum level, electromagnetic radiation is produced when the wavepacket of a charged particle oscillates or otherwise accelerates. Charged particles in a stationary state do not move, but a superposition of such states may result in oscillation, which is responsible for the phenomenon of radiative transition between quantum states of a charged particle.

Depending on the circumstances, electromagnetic radiation may behave as a wave or as particles. As a wave, it is characterized by a velocity (the speed of light),wavelength, and frequency. When considered as particles, they are known as photons, and each has an energy related to the frequency of the wave given by Planck'srelation E = hν, where E is the energy of the photon, h = 6.626 × 10−34 J·s is Planck's constant, and ν is the frequency of the wave.

  • One rule is always obeyed regardless of the circumstances: EM radiation in a vacuum always travels at the speed of light, relative to the observer, regardless of the observer's velocity. (This observation led to Albert Einstein's development of the theory of special relativity.)
  • In a medium (other than vacuum), velocity factor or refractive index are considered, depending on frequency and application. Both of these are ratios of the speed in a medium to speed in a vacuum.
thermal radiation and electromagnetic radiation as a form of heat
Thermal radiation and electromagnetic radiation as a form of heat
  • The basic structure of matter involves charged particles bound together in many different ways. When electromagnetic radiation is incident on matter, it causes the charged particles to oscillate and gain energy. The ultimate fate of this energy depends on the situation. It could be immediately re-radiated and appear as scattered, reflected, or transmitted radiation. It may also get dissipated into other microscopic motions within the matter, coming tothermal equilibrium and manifesting itself as thermal energy in the material. With a few exceptions such as fluorescence, harmonic generation,photochemical reactions and the photovoltaic effect, absorbed electromagnetic radiation simply deposits its energy by heating the material. This happens both for infrared and non-infrared radiation. Intense radio waves can thermally burn living tissue and can cook food. In addition to infrared lasers, sufficiently intense visible and ultraviolet lasers can also easily set paper afire. Ionizing electromagnetic radiation can create high-speed electrons in a material and break chemical bonds, but after these electrons collide many times with other atoms in the material eventually most of the energy gets downgraded to thermal energy, this whole process happening in a tiny fraction of a second. That infrared radiation is a form of heat and other electromagnetic radiation is not, is a widespread misconception in physics. Any electromagnetic radiation can heat a material when it is absorbed.

The inverse or time-reversed process of absorption is responsible for thermal radiation. Much of the thermal energy in matter consists of random motion of charged particles, and this energy can be radiated away from the matter. The resulting radiation may subsequently be absorbed by another piece of matter, with the deposited energy heating the material. Radiation is an important mechanism of heat transfer.

  • The electromagnetic radiation in an opaque cavity at thermal equilibrium is effectively a form of thermal energy, having maximum radiation entropy. Thethermodynamic potentials of electromagnetic radiation can be well-defined as for matter. Thermal radiation in a cavity has energy density .
types of electromagnetic wave
Types of Electromagnetic Wave
  • Light, microwaves, x-rays, and TV and radio transmissions are all kinds of electromagnetic waves. They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength.

Electromagnetic waves can be described in terms of three basic parameters:

  • Velocity (c)
  • Wavelength (λ)
  • Frequency (f)
  • The following relationship exists between the above three parameters:
  • λf= c = 3.8 x108m/sec
  • Where λ is in metres and f is in hertz.

Electromagnetic radiation effects approach in a wide range of wavelengths. This electromagnetic radiation range is broken behind aware keen on a numeral of dissimilar group, every of that divide definite possessions.


Long radio waves:

  • That include the deprived occurrence with uses of wavelength at times contain occurrence smaller amount than 1 Hertz with wavelengths during surplus of 1 kilometre.

Short radio waves:

  • That have privileged occurrence with also minute wavelength. Frequently uses in extremely short-range broadcasting communication.


  • That is difficult event influence hypocritical approximately among broadcasting with infrared waves.

Infrared radiation:

  • Thatradiation is the part of the electromagnetic spectrum use immediately under scarlet beam within conditions of occurrence.

Ultraviolet light:

  • That is further than violet beam during situation of occurrence. Its major use of organization is the sun also further leading light. It is formed through electric-curve light for technological function.

X rays:

  • Thatalso recognized are divided keen on two categories: soft also hard X rays. Soft X rays consist of lengthy wavelengths and are quicker to the ultraviolet group of the spectrum. Hard X rays are faster toward the gamma-ray collection of the spectrum with comprising a lot undersized wavelengths.

Gamma rays:

  • Thatis the small wavelength, high event category of electromagnetic energy. They are fundamentally uses equal toward X rays during their consequence, excluding are formed through energized basis as a substitute of internal electrons.

An Ideal remote sensing system shown in Figure 1, consists of the following basic stages:

  • Electromagnetic energy source
  • Energy propagation
  • Energy interaction\Return signal
  • Recording
  • Supply of information in the desired form.

The source of energy produces electromagnetic energy and it propagates from the source to a homogeneous target.

  • In ideal case, produced electromagnetic energy contains all wavelengths and there is no loss of energy during propagation.
  • When the energy interacts with the target, depending upon the characteristics of the target, the energy is transmitted, absorbed scattered emitted, or reflected from the target to the sensor.

The energy from the target to the sensor is in the form of return signal, reaching a linear sensor which responds linearly to electromagnetic energy of all wavelengths and intensity. The return signal is recorded and processes in real time by the data recorder. The data is then processed into a format which is useful for interpretation. T

  • he information about the target collected is made available to the users in the desired form.
  • Radar, like sonar and seismology, uses a man-made pulse of radio energy to map distance based on the length of time it takes the pulse to return from the source.
  • Radar (short for "Radio Detection and Ranging"), which can be airborne or spaceborne, has greatly changed the way we see the land and ocean surfaces.

Radar is based on the principle of sending very long wavelength radiation (called microwaves) from an antenna, and then detecting that energy after it bounces off a remote target.

  • The wavelength of the microwave, its polarization (vertical or horizontal orientation) and strength can be controlled at the source and measured when it returns.
  • Many common land-cover types and materials affect the polarity and strength of the radar return differently, which helps in their identification
electromagnetic radiation and health
Electromagnetic radiation and health
  • Electromagnetic radiation can be classified into ionizing radiation and non-ionizing radiation, based on whether it is capable of ionizing atoms and breaking chemical bonds. Ultraviolet and higher frequencies, such as X-rays or gamma rays are ionizing. These pose their own special hazards: see radiation and radiation poisoning.
  • Non-ionizing radiation, discussed here, is associated with two major potential hazards: electrical and biological. Additionally, induced electric current caused by radiation can generate sparks and create a fire or explosive hazard.
types of hazards
Types of hazards
  • the oscillating electric and magnetic fields in electromagnetic radiation will induce an electric current in any conductor through which it passes. Strong radiation can induce current capable of delivering an electric shock to persons or animals. It can also overload and destroy electrical equipment. The induction of currents by oscillating magnetic fields is also the way in which solar storms disrupt the operation of electrical and electronic systems, causing damage to and even the explosion of power distribution transformers,[1] blackouts (as in 1989), and interference with electromagnetic signals (e.g. radio, TV, and telephone signals).[2]

Fire hazards

  • Extremely high power electromagnetic radiation can cause electric currents strong enough to create sparks (electrical arcs) when an induced voltage exceeds the breakdown voltage of the surrounding medium (e.g. air). These sparks can then ignite flammable materials or gases, possibly leading to an explosion.
  • This can be a particular hazard in the vicinity of explosives or pyrotechnics, since an electrical overload might ignite them. This risk is commonly referred to as HERO (Hazards of Electromagnetic Radiation to Ordnance). MIL-STD-464A mandates assessment of HERO in a system, but Navy document OD 30393 provides design principles and practices for controlling electromagnetic hazards to ordnance.
  • On the other hand, the risk related to fueling is known as HERF (Hazards of Electromagnetic Radiation to Fuel). NAVSEA OP 3565 Vol. 1 could be used to evaluate HERF, which states a maximum power density of 0.09 W/m² for frequencies under 225 MHz (i.e. 4.2 meters for a 40 W emitter).

Biological hazards

  • The best understood biological effect of electromagnetic fields is to cause dielectric heating. For example, touching or standing around an antenna while a high-power transmitter is in operation can cause severe burns. These are exactly the kind of burns that would be caused inside a microwave oven.
  • This heating effect varies with the power and the frequency of the electromagnetic energy. A measure of the heating effect is thespecific absorption rate or SAR, which has units of watts per kilogram (W/kg). The IEEE[3] and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR, mainly based onICNIRP Guidelines,[4] which guard against thermal damage.
  • There are publications which support the existence of complex biological effects of weaker non-thermal electromagnetic fields (see Bioelectromagnetics), including weak ELF magnetic fields.[5][6] and modulated RF and microwave fields[7] Fundamental mechanisms of the interaction between biological material and electromagnetic fields at non-thermal levels are not fully understood.[8]
  • DNA fragmentation. A 2009 study at the University of Basel in Switzerland found that intermittent (but not continuous) exposure of human cells to a 50 Hz electromagnetic field at a flux density of 1 mT (or 10 G) induced a slight but significant increase of DNA fragmentation in the Comet assay.[9] However that level of exposure is already above current established safety exposure limits.
positions of governments and scientific bodies
Positions of governments and scientific bodies
  • World Health Organization
  • "The Task Group concluded that there are no substantive health issues related to ELF electric fields at levels generally encountered by members of the public.... [O]n balance, the evidence [about magnetic fields being] related to childhood leukaemia is not strong enough to be considered causal.... A number of other adverse health effects have been studied for possible association with ELF magnetic field exposure. These include other childhood cancers, cancers in adults, depression, suicide, cardiovascular disorders, reproductive dysfunction, developmental disorders, immunological modifications, neurobehavioural effects and neurodegenerative disease. The WHO Task Group concluded that scientific evidence supporting an association between ELF magnetic field exposure and all of these health effects is much weaker than for childhood leukaemia. In some instances (i.e. for cardiovascular disease or breast cancer) the evidence suggests that these fields do not cause them."[10]

Mobile phone radiation and health concerns have been raised, especially following the enormous increase in the use of wireless mobile telephony throughout the world (as of August 2005, there were more than 2 billion users worldwide). Mobile phones use electromagnetic radiation in the microwave range, and some[39][unreliable medical source?] believe this may be harmful to human health. These concerns have induced a large body of research (both epidemiological and experimental, in non-human animals as well as in humans). Concerns about effects on health have also been raised regarding other digital wireless systems, such as data communication networks.

  • TheWorld Health Organization, based upon the consensus view of the scientific and medical communities, states that health effects (e.g. headaches or promotion of cancer) are unlikely to be caused by cellular phones or their base stations,[40][41] and expects to make recommendations about mobile phones in the third quarter of 2010 at the earliest, or the first quarter of 2011 at the latest.[42]

U.S. military definition

  • In Federal Standard 1037C, the United States government adopts thefollowingdefinition:
  • Electromagnetic radiation hazards (RADHAZ or EMR hazards): Hazards caused by a transmitter/antenna installation that generates electromagnetic radiation in the vicinity of ordnance, personnel, or fueling operations in excess of established safe levels or increases the existing levels to a hazardous level; or a personnel, fueling, or ordnance installation located in an area that is illuminated by electromagnetic radiation at a level that is hazardous to the planned operations or occupancy.

These hazards will exist when an electromagnetic field of sufficient intensity is generated to: (a) induce or otherwise couple currents and/or voltages of magnitudes large enough to initiate electroexplosive devices or other sensitive explosive components of weapon systems, ordnance, or explosive devices; (b) cause harmful or injurious effects to humans and wildlife; (c) create sparks having sufficient magnitude to ignite flammable mixtures of materials that must be handled in the affected area. —Department of Defense Dictionary of Military and Associated Terms

conelrad contal electromagnetic radiation
CONELRAD (Contal Electromagnetic Radiation)
  • CONELRAD (Control of ElectromagneticRadiation) was a method of emergencybroadcasting to the public of the United States in the event of enemy attack during the Cold War. It was intended to serve two purposes; to prevent Sovietbombers from homing in on American cities by usingradio or TV stations as beacons, and to provide essential civil defenseinformation.U.S. PresidentHarry S. Trumanestablished CONELRAD in 1951.

After the development of intercontinental ballistic missiles reduced the likelihood of a bomber attack, CONELRAD was replaced by the Emergency Broadcast System on August 5, 1963, which was later replaced with the Emergency Alert System in 1997; all were administered by the Federal Communications Commission(FCC).[1]

  • Unlike its successors, the EBS and EAS, CONELRAD was never used for nor intended to be used for severe weather warnings or local civil emergencies.

ONELRAD concept was originally known as theKey Station System. According to an FCC document created during the "Informal Government - Industry Technical Conference" on March 26, 1951


In the event of an emergency, all United States television and FMradio stationswere required to stop broadcasting. Upon alert, most AM medium wave stations shut down. The stations that stayed on the air would transmit on either 640 or 1240 kHz. They would transmit for several minutes, and then go off the air and another station would take over on the same frequency in a "round robin" chain. This was to confuse enemy aircraft who might be navigating using Radio Direction Finding. By law, radio sets manufactured between 1953 and 1963 had these frequencies marked by the triangle-in-circle ("CD Mark") symbol of Civil Defense.


In the event of an emergency, all United States television and FMradio stationswere required to stop broadcasting. Upon alert, most AM medium wave stations shut down. The stations that stayed on the air would transmit on either 640 or 1240 kHz. They would transmit for several minutes, and then go off the air and another station would take over on the same frequency in a "round robin" chain. This was to confuse enemy aircraft who might be navigating using Radio Direction Finding. By law, radio sets manufactured between 1953 and 1963 had these frequencies marked by the triangle-in-circle ("CD Mark") symbol of Civil Defense.[3]

  • "CD Mark" symbols like this (though generally shown as simple white triangles) were on every radio sold in the U.S., at the 640 kHz and 1240 kHz frequency points, to help listeners find the CONELRAD stations.