Whatischargepolarization

In contrast to fluorescence, Raman scattering is not a resonance phenomenon, but the scattering occurs here (as in Rayleigh scattering) via virtual levels. Raman scattering consequently also occurs for photon energy levels outside of resonance to an atomic or molecular electronic transition.

A radio wave is composed of one electric and one magnetic field that oscillates in a repeating pattern. Polarization describes the way the electric field of the radio wave is oriented. In some cases, especially waves that are generated by a natural source, the fields vibrate in multiple random orientations, and are said to be unpolarized. But when waves are generated from, or passed through an intentionally polarizing device, such as  an antenna, the fields are restricted in movement and are said to be “polarized.”

Chargepolarization simpledefinition

In general, it’s better to keep the orientations of the two antennas matched. Reception is best when the receiving antenna is not in a position that prevents the polarization from being too far off from the transmitting antenna, though it rarely needs to be exact.

Raman scattering of molecules is characterized by a very small scattering cross-section. Consequently, a rather high concentration of molecules is needed to obtain detectable signals. Therefore, Raman spectra for single molecules are not possible. However, if the molecule is close to a metallic surface (e.g., made of silver, copper, or gold), this can extremely amplify the Raman signal. This so-called surface-enhanced Raman scattering (SERS) is used, for example, in surface-enhanced Raman spectroscopy and surface-enhanced resonance Raman spectroscopy (SERRS).In the quantum mechanical model, the Raman effect can be described as a two-photon transition between quantized energy levels. Thus, Raman control occurs when photons interact with a molecule and the molecule is placed in a virtual higher energy state. This higher energy state can result in a few different outcomes, such as the molecule relaxing to a new vibrational energy state. Thus, a photon with a different level of energy is created. In this case, the difference between the energy of the incident photon and the energy of the scattered photon is called the Raman shift. When the interaction of the molecule with light leads to a shift in the electron cloud around the molecule, this also changes its polarizability.In plasma physics, the Raman effect describes scattering by plasma waves, in which the light amplifies the plasma wave during the scattering process and heats up the plasma (Raman instability).

Alex Milne was Product Marketing Manager and Digital Marketing Manager for RF Venue, and a writer for the RF Venue Blog, from 2014-2017. He is founder and CEO of Terraband, Inc., a networking and ICT infrastructure company based in Brooklyn, NY., and blogs on spectrum management, and other topics where technology,...

Note: The most important difference between Rayleigh and Raman scattering is the elasticity of Rayleigh scattering - whereas Raman scattering is inelastic. In (elastic) Rayleigh scattering, the kinetic energy of the random particles of the system in which the scattering occurs remains the same. Consequently, the frequency of the incident light coincides with that of the scattered light. On the other hand, when (inelastic) Raman scattering occurs, the kinetic energy of the random particles changes. Consequently, the incident light has a different frequency than the light scattered by Raman scattering.

Electricpolarization simpledefinition

Wave polarization is not a particularly easy concept to visualize. It takes place in three dimensions and across time. Polarized waves have a fixed, constant orientation and create a path that is shaped like a flat plane as it travels through space, and have what we refer to today as linear polarization. The first 40 seconds of this video show linear polarization.

Relation betweenpolarizationand electric field

Helical antennas are the most frequently seen circularly polarized antennas in the pro sound world. “Helicals” can produce a circularly polarized beam with high gain by using a carefully modeled spiral construction that produces either right handed (clockwise spin), or left handed (counter clockwise) polarization to the signal. Helicals are useful as a receiving antenna, since they pick up incoming waves of any polarization to the same degree. Shifts in orientation from a handheld or beltpack transmitter are less likely to cause the drop-outs which very often happen when a performer moves to a less favorable polarization.

The more common antenna types are linearly polarized, like dipoles, whips and LPDAs. But you won’t hear the term linear polarization thrown around at an equipment store. Instead, we get some antenna terms from the linearly polarized types: when the linear plane is perpendicular to the ground, it is said to be vertically polarized. When that plane is parallel with the ground, it is horizontally polarized. But really, these terms are arbitrarily based on the human perception of up or down in relation to the earth and gravity, not some physical constant.

*RF Venue has incorporated this little known technique in the Diversity Fin antenna. Read more at Mike Benonis’ paper. Video courtesy of "Ruff."

Electricpolarizationformula

Even though polarization is initiated predominately by the transmitting antenna, radio wave polarization can change dramatically when reflecting off objects in the environment, such as walls and floors. The result is uncertainty about which orientation a particular radio wave will be when it reaches the receiver antenna, and there is always a chance that a condition called “crossed polarization” will occur: When that happens, a noise burst is briefly (but noticeably) heard. No one wants that. To avoid crossed polarization fades, you can use a technique known as polarization diversity by orienting two antennas closely together, but oriented 90 degrees from each other.* This makes it very likely that a given radio wave will be picked up by at least one of the antennas at all times.

There can also be circular polarization, which, unlike in linearly polarized radio waves, the electric field also spins along an axis, sort of like a twisted ribbon. The final half of the video demonstrate this.

Raman scattering is a form of inelastic scattering of light or other electromagnetic radiation by electrons, atoms, or molecules. Raman scattering can occur when light enters gases, plasmas as well as crystalline solids (phonon Raman scattering), and is due to the interaction of photons with the relevant particles of the medium involved. Such interactions concern, for example, rotational and vibrational energy in molecules or energy quanta of lattice vibration (optical or acoustic) phonons, in solids. In molecules or crystals, energy transfer can occur between the exciting photon and the excited matter, so that the rotational and vibrational energy of the involved molecule or the vibrational energy in the crystal lattice changes - i.e. there is a transition of the molecule from one energy level to another.The term "inelastic" describes the fact that this type of scattering changes the kinetic energy of the particles involved. So there is an energy transfer between the radiant energy and the scattering medium, where the scattered light has a higher or lower frequency than the incident light beam. So there is an energy transfer between the radiant energy and the scattering medium, where the scattered light has a higher or lower frequency than the incident light beam. The respective frequency is specific for the scattering atom or molecule. If the frequency of the exciting photon is resonant with an electronic transition in the molecule or crystal, the scattering efficiency is increased by two to three orders of magnitude (resonance Raman effect). In the case of such inelastic scattering, the energy balance causes a frequency shift of the scattered light. Both directions of energy transfer are possible.