High Frequency Electromagnetic Fields April 5, 2007Posted by healthyself in Amplified Signals, Amplitude, Antennas, Blogroll, Cable, Cell Masts, Cell phone industry, Cell phone safety, Cell Phones, Computer Rooms, Cordless Phones, Definitions, Digital, Distribution, Electrical Components, Electrical Pulses, Electrical Wiring, Electromagnetic Communications, Electromagnetic Field, Electromagnetic Interference, Electromagnetic pollution, Electromagnetic Radiation, Electromagnetic Spectrum, Electromagnetic waves, Electrosensitivity, Electrosmog, ELF, Emergency Medicine, EMF Research, EMF's, EMR, Energy, Environment, Epidemiology, Exposure, Frequencies, GHz, Government's role, HF, High Frequencies, high voltage transmission lines, Homes, HOuseholds, HRD, Human Resources, Hz, Infrared, Interdisciplinary, Landline, Laptops, Legal Issues, Lifestyle, Low Frequencies, MCS, MF, MHz, Microwave exposure, Mitigation, mobile telephones, Oscillate, Pulsed Radiation, Pulses, Radar, radiation, Radio Frequency Radiation, Radio Waves, Radios, Research Needed, Resonant Frequency, Risk of Disease, Sound, Speakerphones, Telecommunications, Telephony, Transducer, Transfer, transmission, UHF, VDT, VLF, W/Kg, W/m2, watts, Wave Front, Waves, Who is Affected?, WiFi, Wired, Wired Phone, Wireless, Wireless Phones, Workplace, X-Rays.
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“Mobile telephones, television and radio transmitters and radar produce RF fields. These fields are used to transmit information over long distances and form the basis of telecommunications as well as radio and television broadcasting all over the world. Microwaves are RF fields at high frequencies in the GHz range. In microwaves ovens, we use them to quickly heat food.”"At radio frequencies, electric and magnetic fields are closely interrelated and we typically measure their levels as power densities in watts per square metre (W/m2).”
- The electromagnetic spectrum encompasses both natural and human-made sources of electromagnetic fields.
- Frequency and wavelength characterise an electromagnetic field. In an electromagnetic wave, these two characteristics are directly related to each other: the higher the frequency the shorter the wavelength.
- Ionizing radiation such as X-ray and gamma-rays consists of photons which carry sufficient energy to break molecular bonds. Photons of electromagnetic waves at power and radio frequencies have much lower energy that do not have this ability.
- Electric fields exist whenever charge is present and are measured in volts per metre (V/m). Magnetic fields arise from current flow. Their flux densities are measured in microtesla (µT) or millitesla (mT).
- At radio and microwave frequencies, electric and magnetic fields are considered together as the two components of an electromagnetic wave. Power density, measured in watts per square metre (W/m2), describes the intensity of these fields.
- Low frequency and high frequency electromagnetic waves affect the human body in different ways.
- Electrical power supplies and appliances are the most common sources of low frequency electric and magnetic fields in our living environment. Everyday sources of radiofrequency electromagnetic fields are telecommunications, broadcasting antennas and microwave ovens.”
How is the Electromagnetic Radiation Measured? October 16, 2006Posted by healthyself in Blogroll, Definitions, Electrical Components, Electrical Pulses, Electrical Surges, Electrical Wiring, Electromagetic pollution, electromagnetic, Electromagnetic Communications, Electromagnetic Field, Electromagnetic Interference, Electromagnetic pollution, Electromagnetic Spectrum, Electromagnetic waves, Electrosensitivity, Electrosmog, ELF, EMF's, EMR, Environment, Exposure, Frequencies, GHz, Global Warming, Government's role, HF, High Frequencies, high voltage transmission lines, HOuseholds, Hz, Infrared, LF, Lifestyle, light beam, Low Frequencies, MF, MHz, Microwave exposure, Pulsed Radiation, Pulses, Quantum Waves, radiation, Radio Waves, Radios, Sound, Spectrum, transmission, Ultraviolet, Unified Field, Visible Light, VLF, Waves.
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…The electromagnetic (EM) spectrum is …types of radiation … as a group. Radiation is energy that travels and spreads out as it goes– visible light …. from a lamp….or radio waves .. or from a radio station are two types of electromagnetic radiation. Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays. Here are the different types of radiation in the EM spectrum, in order from lowest energy to highest:
|Radio: …this is the same kind of energy that radio stations emit into the air …to capture and turn into your favorite Mozart, Madonna, or Coolio tunes. But radio waves are also emitted by other things … such as stars and gases in space…|
|Microwaves: … will cook your popcorn in just a few minutes! In space, microwaves are used by astronomers to learn about the structure of nearby galaxies, including our own Milky Way!|
|Infrared: we often think of this as being the same thing as ‘heat’, because it makes our skin feel warm. In space, IR light maps the dust between stars. Visible:…this is the part that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars … also by fast-moving particles hitting other particles.
Ultraviolet: we know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn! Stars and other “hot” objects in space emit UV radiation.
|X-rays: your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the Universe also emit X-rays .|
|Gamma-rays: radioactive materials (some natural and others made by man in things like nuclear power plants) can emit gamma-rays. Big particle accelerators that scientists use to help them understand what matter is made of can sometimes generate gamma-rays. But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways.|
A Radio Wave is not a Gamma-Ray, a Microwave is not an X-ray … or is it?
|Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing, electromagnetic radiation.|
We may think that radio waves are completely different physical objects or events than gamma-rays. They are produced in very different ways, and we detect them in different ways. But are they really different things? The answer is ‘no’. Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing. They are all electromagnetic radiation.
Electromagnetic radiation can be described in terms of a stream of photons, which are massless particles each traveling in a wave-like pattern and moving at the speed of light. Each photon contains a certain amount (or bundle) of energy, and all electromagnetic radiation consists of these photons. The only difference between the various types of electromagnetic radiation is the amount of energy found in the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and … the most energetic of all … gamma-rays.
|The electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency.|
“Actually, the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. So why do we have three ways of describing things, each with a different set of physical units? After all, frequency is measured in cycles per second (which is called a Hertz), wavelength is measured in meters, and energy is measured in electron volts.”
“The answer is that scientists don’t like to use big numbers when they don’t have to. It is much easier to say or write “two kilometers or 2 km” than “two thousand meters or 2,000 m”. So generally, scientists use whatever units are easiest for whatever they are working with. In radio astronomy, astronomers tend to use wavelengths or frequencies. This is because most of the radio part of the EM spectrum falls in the range from a about 1 cm to 1 km (30 gigahertz (GHz) to 100 kilohertz (kHz)). The radio is a very broad part of the EM spectrum. Infrared astronomers also use wavelength to describe their part of the EM spectrum. They tend to use microns (or millionths of meters) for wavelengths, so that they can say their part of the EM spectrum falls in the range 1 to 100 microns. Optical astronomers use wavelengths as well. In the older “CGS” version of the metric system, the units used were angstroms. An angstrom is equal to 0.0000000001 meters (10-10 m in scientific notation)! In the newer “SI” version of the metric system, we think of visible light in units of nanometers or 0.000000001 meters (10-9 m). In this system, the violet, blue, green, yellow, orange, and red light we know so well has wavelengths between 400 and 700 nanometers. This range is only a small part of the entire EM spectrum, so you can tell that the light we see is just a little fraction of all the EM radiation around us! By the time you get to the ultraviolet, X-ray, and gamma-ray regions of the EM spectrum, lengths have become too tiny to think about any more. So scientists usually refer to these photons by their energies, which are measured in electron volts. Ultraviolet radiation falls in the range from a few electron volts (eV) to a about 100 eV. X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-rays then are all the photons with energies greater than 100 keV.
Why Do We Have to Go to Space to See All of the Electromagnetic Spectrum?
Electromagnetic radiation from space is unable to reach the surface of the Earth except at a very few wavelengths, such as the visible spectrum, radio frequencies, and some ultraviolet wavelengths. Astronomers can get above enough of the Earth’s atmosphere to observe at some infrared wavelengths from mountain tops or by flying their telescopes in an aircraft. Experiments can also be taken up to altitudes as high as 35 km by balloons which can operate for months. Rocket flights can take instruments all the way above the Earth’s atmosphere for just a few minutes before they fall back to Earth, but a great many important first results in astronomy and astrophysics came from just those few minutes of observations. For long-term observations, however, it is best to have your detector on an orbiting satellite … and get above it all!
What are the Wavelengths of the Electromagnetic Spectrum? September 27, 2006Posted by healthyself in Blogroll, Cell phone safety, Definitions, Distribution, Electromagnetic Communications, Electromagnetic Field, Electromagnetic Interference, Electromagnetic pollution, Electromagnetic Spectrum, Electromagnetic waves, Electrosensitivity, Electrosmog, ELF, EMR, Endogenous Fields, Environment, Frequencies, Gamma Rays, Infrared, Light, Microwave exposure, mobile telephones, Noise, particle, Radio Waves, Radios, Sound, Spectrum, Telecommunications, Telephony, transmission, UHF, Ultraviolet, VDT, Visible Light, X-Rays.
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“The electromagnetic spectrum is the distribution of electromagnetic radiation according to energy (or equivalently, by virtue of the relations in the previous section, according to frequency or wavelength).”
Regions of the Electromagnetic Spectrum
“The following table gives approximate wavelengths, frequencies, and energies for selected regions of the electromagnetic spectrum.”
|Spectrum of Electromagnetic Radiation|
The notation “eV” stands for electron-volts, a common unit of energy measure in atomic physics. A graphical representation of the electromagnetic spectrum is shown in the figure below.
|The electromagnetic spectrum|
“Thus we see that visible light and gamma rays and microwaves are really the same things. They are all electromagnetic radiation; they just differ in their wavelengths.”
The Spectrum of Visible Light
The visible part of the spectrum may be further subdivided according to color, with red at the long wavelength end and violet at the short wavelength end, as illustrated (schematically) in the following figure.
|The visible spectrum|
What is the Electromagnetic Spectrum? September 21, 2006Posted by healthyself in Blogroll, Cell phone safety, Color, Definitions, Electromagnetic Field, Electromagnetic waves, Frequencies, Gamma Rays, Infrared, Light, light beam, Low Frequencies, Magnetic, MHz, Microwave exposure, Oscillate, Photons, Radio Waves, Spectrum, Visible Light.
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“..Electromagnetic radiation can be described in terms of a stream of photons, each traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy. … the only difference between radio waves, visible light, and gamma-rays is the energy of the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and gamma-rays.”"Actually, the amount of energy a photon has makes it sometimes behave more like a wave and sometimes more like a particle. This is called the “ wave-particle duality” of light. …only in how it behaves. Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles. …the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. The relationships are:
the wavelength equals the speed of light divided by the frequency
lambda = c / nu” http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html