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Articles ~ Ghost hunting and beyond ~ Understanding Electromagnetism |
Characteristics of Electromagnetic Phenomena 1. Static may be only solitarily, not oscillating electric and magnetic fields (MF). All fields are vectorial units (have a x, y, z component). • Electric field E = U/d (unit: V/m) • Magnetic field H = I/d (unit: A/m) • Magnetic Induction B = H ·m0 ·mr (unit: 1 T (Tesla) = 104 G) All magnetic field lines must close themselves (equation: div B = 0) 2. Electromagnetic Radiation consists of rightangular orientated vectors of electric and magnetic field strengths oscillating with frequency f. They spread out with the speed of light c ,have the wavelength l = c/f and the Energy E=h·f . • "Non ionizing" means: Generating no charge separation on atomic level • "Non thermal" means: Absorbance causes no warming up, energy below the thermodynamical equilibrium. 3. Frequency range of EMF: ULF (ultra low freq. <1 Hz) ELF (extremely low freq. 1 -300 Hz) VLF (very low freq. 0.3-100 KHz) VHF (very high freq. 100-500 KHz) UHF (ultra high freq. >500-1000 MHz) EHF (extremely high freq. >1 GHz) Also Radio band assignments are used (NF, HF, LW, MW, KW, UKW)
Man made Sources of MF and EMF • Power-lines and -consumers (16.33, 50, 60 Hz ELF). • Cable communications (e.g. Telephone, Computer networks ELF-VHF). • Radio communication, medicine, navigation and positioning (e.g. Broadcast, TV, Tomograhy, Radio-telephony, Cellular telephones (900 MHz-2.1 GHz), Radar VHF-EHF). Natural Sources of MF and EMF
Wavelength and frequencyAny wave—including an electromagnetic wave—can be described by two properties: its wavelength and frequency. The wavelength of a wave is the distance between two successive identical parts of the wave, as between two wave peaks or crests. The Greek letter lambda (λ) is often used to represent wavelength. Wavelength is measured in various units, depending on the kind of wave being discussed. For visible light, for example, wavelength is often expressed in nanometers (billionths of a meter); for radio waves, wavelengths are usually expressed in centimeters or meters. Frequency is the rate at which waves pass a given point. The frequency of an X-ray beam, for example, might be expressed as 1018 hertz. The term hertz (abbreviation: Hz) is a measure of the number of waves that pass a given point per second of time. If you could watch the X-ray beam from some given position, you would see 1,000,000,000,000,000,000 (that is, 1018) wave crests pass you every second. For every electromagnetic wave, the product of the wavelength and frequency equals a constant, the speed of light (c). In other words, λ · f = c. This equation shows that wavelength and frequency have a reciprocal relationship to each other. As one increases, the other must decrease. Gamma rays, for example, have very small wavelengths and very large frequencies. Radio waves, by contrast, have large wavelengths and very small frequencies.
Other waveforms are often called composite waveforms and can often be described as a combination of a number of sinusoidal waves or other basis functions added together. The Fourier series describes the decomposition of periodic waveforms, such that any periodic waveform can be formed by the sum of a fundamental component and harmonic components. Finite-energy non-periodic waveforms can be analyzed into sinusoids by the Fourier transform. Electromagnetism and Life There are many theoretical foundations for the interaction between electro-magnetism and life.
Behavior of electromagnetic fields The behavior of the electromagnetic field can be resolved into four different parts of a loop: (1) the electric and magnetic fields are generated by electric charges, (2) the electric and magnetic fields interact only with each other, (3) the electric and magnetic fields produce forces on electric charges, (4) the electric charges move in space. The feedback loop can be summarized in a list, including phenomena belonging to each part of the loop:
Phenomena in the list are marked with a star () if they consist of magnetic fields and moving charges which can be reduced by suitable Lorentz transformations to electric fields and static charges. This means that the magnetic field ends up being (conceptually) reduced to an appendage of the electric field, i.e. something which interacts with reality only indirectly through the electric field. There are different mathematical ways of representing the electromagnetic field. The first one views the electric and magnetic fields as three-dimensional vector fields. These vector fields each have a value defined at every point of space and time and are thus often regarded as functions of the space and time coordinates. As such, they are often written as E (x, y, z, t) (electric field) and B(x,y,z,t) (magnetic field). If only the electric field () is non-zero, and is constant in time, the field is said to be an electrostatic field. Similarly, if only the magnetic field () is non-zero and is constant in time, the field is said to be a magnetostatic field. However, if either the electric or magnetic field has a time-dependence, then both fields must be considered together as a coupled electromagnetic field using Maxwell's equations[1]. With the advent of special relativity, physical laws became susceptible to the formalism of tensors. Maxwell's equations can be written in tensor form, generally viewed by physicists as a more elegant means of expressing physical laws. The behaviour of electric and magnetic fields, whether in cases of electrostatics, magnetostatics, or electrodynamics (electromagnetic fields), is governed in a vacuum by Maxwell's equations. In the vector field formalism, these are: The Lorentz force law governs the interaction of the electromagnetic field with charged matter. Sources: http://www.scienceclarified.com/ http://en.wikipedia.org/ |