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Topic: Atmospheric diffraction

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Bragg diffraction

Diffraction

Nonlinear optics

	Diffraction Summary
		Diffraction from multiple slits, as described above, is similar to what occurs when waves are scattered from a periodic structure, such as atoms in a crystal or rulings on a diffraction grating.
		Bragg diffraction is used in X-ray crystallography to deduce the structure of a crystal from the angles at which X-rays are diffracted from it.
		The most common demonstration of Bragg diffraction is the spectrum of colors seen reflected from a compact disc: the closely-spaced tracks on the surface of the disc form a diffraction grating, and the individual wavelengths of white light are diffracted at different angles from it, in accordance with Bragg's law.
	www.bookrags.com /Diffraction (3160 words)

	Diffraction - Wikipedia, the free encyclopedia
		Diffraction also occurs when any group of waves of a finite size is propagating; for example, a narrow beam of light waves from a laser must, because of diffraction of the beam, eventually diverge into a wider beam at a sufficient distance from the laser.
		Diffraction is one particular type of wave interference, caused by the partial obstruction or lateral restriction of a wave.
		The most common demonstration of Bragg diffraction is the spectrum of colors seen reflected from a compact disc: the closely-spaced tracks on the surface of the disc form a diffraction grating, and the individual wavelengths of white light are diffracted at different angles from it, in accordance with Bragg's law.
	en.wikipedia.org /wiki/Diffraction (1581 words)

	Diffraction -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-24)
		Diffraction is one particular type of wave (The act of hindering or obstructing or impeding) interference, caused by the partial obstruction or lateral restriction of a wave.
		Diffraction will not occur if the wave is not (additional info and facts about coherent) coherent, and diffraction effects become weaker (and ultimately undetectable) as the size of obstruction is made larger and larger compared to the wavelength.
		Diffraction is not the same as (The change in direction of a propagating wave (light or sound) when passing from one medium to another) refraction, although both are phenomena in which a wave does not propagate in a single direction.
	www.absoluteastronomy.com /encyclopedia/d/di/diffraction.htm (1620 words)

	Diffraction - Open Encyclopedia (Site not responding. Last check: 2007-10-24)
		In physics, diffraction is a wave phenomenon: the apparent bending and spreading of waves when they meet an obstruction.
		Diffraction occurs with electromagnetic waves, such as light and radio waves, and also in sound waves and water waves.
		In addition to diffraction of classical waves, it is also possible, due to wave-particle duality, to observe diffraction of particles such as neutrons or electrons.
	www.open-encyclopedia.com /Diffraction (1099 words)

	[No title]
		In reality, even with no atmospheric turbulence, the light from a star is spread out into a point spread function in which 84 percent of the light falls into a central maximum called the Airy disk (Figure 1).
		The radius of this disk is governed by the diameter of the telescope and the wavelength of the light and is given by the equation a = 1.22 l/D, where l and D are in meters, and a is the angular radius of the image in radians.
		These temperature variations throughout the atmosphere produce optical effects, because the index of refraction depends on the density of the air, and the density depends on the temperature.
	www.spie.org /web/oer/december/adaptive_optics.html (3219 words)

	Diffraction (Site not responding. Last check: 2007-10-24)
		Diffraction also occurs when any of waves of a finite size is for example a narrow beam of light waves from a laser must because of diffraction of the eventually diverge into a wider beam at sufficient distance from the laser.
		Diffraction from multiple slits as described above similar to what occurs when waves are from a periodic structure such as atoms a crystal or rulings on a diffraction grating.
		The most common demonstration of Bragg diffraction the spectrum of colors seen reflected from a compact disc : the closely-spaced tracks on the surface the disc form a diffraction grating and individual wavelengths of white light are diffracted different angles from it in accordance with law.
	www.freeglossary.com /Diffraction (1221 words)

	Diffraction (Site not responding. Last check: 2007-10-24)
		Diffraction also occurs whenany group of waves of a finite size is propagating; for example, a narrow beam of light waves from a laser must, because of diffraction of the beam, eventually diverge into awider beam at a sufficient distance from the laser.
		Bragg diffraction is used in X-raycrystallography to deduce the structure of a crystal from the angles at which X-rays are diffracted from it.
		The most common demonstration of Bragg diffraction is the spectrum of colors seen reflected from a compact disc : the closely-spaced tracks on the surface of the disc form adiffraction grating, and the individual wavelengths of white light are diffracted at different angles from it, in accordance withBragg's law.
	www.therfcc.org /diffraction-20112.html (1019 words)

	Encyclopedia: Diffraction (Site not responding. Last check: 2007-10-24)
		Electron diffraction is a technique used to examine solids by firing a beam of electrons at a sample and observing their deflection.
		Fresnel diffraction is the diffraction pattern obtained a small number of wavelengths away from the diffracting object.
		This effect limits the minimum size d of spot of light formed at the focus of a lens, known as the diffraction limit: A lens is a device for either concentrating or diverging light, usually formed from a piece of shaped glass.
	www.nationmaster.com /encyclopedia/Diffraction (2599 words)

	Atmospheric diffraction (Site not responding. Last check: 2007-10-24)
		Waterloo Centre for Atmospheric Sciences A collaboration among academic, government and private sector atmospheric scientists involved in regional atmospheric modelling, remote sensing and atmospheric aerosol studies.
		Centre for Atmospheric Chemistry (CAC) At the University of York, Ontario, CAC was formed to foster cooperative research in atmospheric chemistry, to take a leading role in Canada in the education of a new generation of qualified atmospheric chemists, and to provide a communications link
		Collaboratory for Atmospheric Science and Technology (CAST) Aim of group is to promote interaction and collaboration between UK atmospheric scientists.
	www.serebella.com /encyclopedia/article-Atmospheric_diffraction.html (416 words)

	Light phenomena (Site not responding. Last check: 2007-10-24)
		Atmospheric dust and smoke particles are considerably larger than the gas molecules but may still be smaller than the wavelengths of visible light and thus also selectively scatter the blue end of the spectrum, but more strongly than the gas molecules.
		The diffraction pattern traces blue light around the edge of the cloud where the droplets are smallest and red light where the drops are uniformly larger.
		Diffraction interference of light rays (the waves are out of synchronisation) produces changes in light intensity which may appear as a series of light / dark bands within, and close to, the primary rainbow.
	www.auf.asn.au /meteorology/section12.html (4049 words)

	Search Encyclopedia.com (Site not responding. Last check: 2007-10-24)
		light -> The Nature of Light The scientific study of the behavior of light is called optics and covers reflection of light by a mirror or other object, refraction by a lens or prism, diffraction of light as it passes by the edge of an opaque object, and interference patterns resulting from diffraction.
		In seismology, waves moving though the earth are caused by the propagation of a disturbance generated by an earthquake or...
		weather weather, state of the atmosphere at a given time and place with regard to temperature, air pressure (see barometer), wind, humidity, cloudiness, and precipitation.
	www.encyclopedia.com /search.asp?target=Atmospheric+diffraction&rc=10&fh=15&fr=11 (549 words)

	Diffraction (Site not responding. Last check: 2007-10-24)
		MAGAZINES Journal of Research of the National Institute of Standards and Technology 9/1/2001 Shirley, Eric L. An algorithm for computing diffraction effects on total power in the case of Fraunhofer diffraction by a circular lens or aperture is derived.
		Powder neutron diffraction data continue to be used for the solution...
		Diffraction is the apparent bending and spreading of waves when they meet an obstruction.
	hallencyclopedia.com /Diffraction (1405 words)

	Resolution and Seeing
		Therefore, AAI's diffraction resolution for its 10-inch (0.25 m) and 24-inch (0.61 m) telescopes would be 0.54 and 0.23 arcseconds, respectively.
		Recall that the zenith angle is the angular distance from the zenith, and equals 90 degrees at the horizon.
		This is especially the case in solar viewing, where the Sun's energy creates significant atmospheric turbulence and seeing in daytime degrades to the 2 to 4+ arcsecond range.
	www.asterism.org /tutorials/tut15-1.htm (610 words)

	graduate courses in atmospheric science (Site not responding. Last check: 2007-10-24)
		Atmospheric statics, thermodynamics of dry and moist air, and atmospheric convective processes.
		Physical Meteorology II Propagation of electromagnetic energy in the atmosphere; radiative transfers; refraction and scattering (Rayleigh and Mie regimes); visibility; optical phenomena; radar equation.
		Atmospheric Dynamics II More advanced treatment of atmospheric dynamics, in particular large-scale energetics of the atmosphere, wave theory, atmospheric instabilities, mesoscale dynamics, tropical and stratospheric dynamics.
	www-das.uwyo.edu /new_students/courses.html (727 words)

	Atmospheric Science
		The requirements include the appointment of a graduate committee early in the second semester of the student’s program and the formulation of satisfactory program and research plans, to be submitted by the student, before the end of the second semester.
		Candidates for the degree are required to demonstrate satisfactory progress and proficiency in the general areas of atmospheric science to their graduate committee during a rigorous qualifying assessment to be conducted no later than the end of the third semester of their program.
		Atmospheric Dynamics I. Development and interpretation of the atmospheric equations of motion, scales of motion, horizontal atmospheric winds, thermal wind equation, circulation and vorticity.
	grad.uwyo.edu /bulletin/gradbulletin/Engrweb/AtmosSci.htm (1089 words)

	Space Physics Group: Review of Mid-Latitude Ionospheric Scintillations - Abstracts
		It is assumed that irregular phase fluctuations are impressed on the wave in travelling through the ionosphere, and that the amplitude fluctuations develop by a diffraction process as the wave propagates in the free space beneath the ionosphere.
		It is shown that any ionizing agent from outside the earth's atmosphere is unlikely to be responsible for the ionospheric irregularities that cause radio-star scintillations, and that the mechanism for their production must be sought in the terrestrial atmosphere.
		Observations of the radio diffraction pattern over the ground, made with three spaced receivers, indicate ionospheric irregularities aligned with their longer dimension along the Earth's magnetic field, and with axial ratios in the range 2-20.
	www.physics.uq.edu.au /sp/abstr1.html (3540 words)

	Application to observational data (Site not responding. Last check: 2007-10-24)
		Aquilae were binned into a histogram, and this is plotted alongside similar histograms calculated for a number of numerical simulations in Figure 3.10.
		Atmospherically degraded short exposures were generated by combining Kolmogorov-like phase perturbations with those in the model used for the telescope aperture.
		Strehl ratios were calculated in the same way for data taken on the star V656 Herculis, and Curve A in Figure 3.12 shows a histogram of the Strehl ratios obtained.
	www.mrao.cam.ac.uk /telescopes/coast/theses/rnt/node41.html (864 words)

	Atmospheric diffraction - Encyclopedia, History, Geography and Biography
		Light passing through thin clouds made up of uniform size water droplets can cause diffraction rings to appear around the sun and moon.
		The photo (right) shows a diffraction ring around the rising sun.
		A layer of thin clouds that caused it, and it dramatically disappeared when the sun rose high enough.
	www.arikah.net /encyclopedia/Atmospheric_Diffraction (136 words)

	Atmospheric Sciences Research Group Home Page
		These phenomena sometimes form in cirrus clouds high in the atmosphere, but they can also be generated by gently falling ice crystals, also known as “diamond-dust”, that nucleate out on clear cold humid days near the surface.
		Diffraction is the process by which light waves passing around an object, such as a cloud particle, constructively and destructively interfere with one another, forming concentric rings around the central light source.
		The blur around a street light on a foggy night or the bright light of a full moon shining through a thin cloud are common corona forming culprits.
	www.gi.alaska.edu /AtmosSci (522 words)

	Atmospheric Science
		Candidates for the degree are required to demonstrate satisfactory progress and proficiency in the general areas of atmospheric science to their graduate committee during a rigorous qualifying assessment to be conducted no later than the end of the third semester of their program.
		Atmospheric Dynamics I. Development and interpretation of the atmospheric equations of motion, scales of motion, horizontal atmospheric winds, thermal wind equation, circulation and vorticity.
		Global atmospheric and oceanic circulations, radiation balance, water balance and hydrologic cycle, energy balance, energy and moisture transport, evaporation and evapotranspiration, energetic processes, and theories of climate change.
	uwadmnweb.uwyo.edu /UWGrad/bulletin/gradbulletin/Engrweb/AtmosSci.htm (1089 words)

	3. ACOUSTICAL CONSIDERATIONS (Site not responding. Last check: 2007-10-24)
		Atmospheric effects refer to: (1) atmospheric absorption, i.e., the sound absorption by air and water vapor; (2) atmospheric refraction, i.e., the sound refraction caused by temperature and wind gradients; and (3) air turbulence.
		Atmospheric absorption: Atmospheric absorption is a function of the frequency of the sound, the temperature, the humidity, and the atmospheric pressure between the source and the receiver.
		Atmospheric refraction: Atmospheric refraction is the bending of sound waves due to wind and temperature gradients.
	www.fhwa.dot.gov /environment/noise/3.htm (5247 words)

	Diffraction Effects (Site not responding. Last check: 2007-10-24)
		As discussed in your lectures, diffraction of light (with a circular aperture) causes point sources of light to appear as disks rather than single points.
		It is a function of the wavelength of the light and the aperture size of the telescope, and is also known as the angular resolution.
		Where theta is the (diffraction limited - see below) angular resolution in radians, lambda is the wavelength of the light, and D is the telescope aperture (both have to be in the same units, e.g.
	www.ulo.ucl.ac.uk /~diploma/diffraction_effects.html (494 words)

	The GSMT Book: Chapter 4, Section 4.6.2 (Site not responding. Last check: 2007-10-24)
		Diffraction and three-dimensional LGSs are sources of higher-order wavefront sensing error, because the Shack-Hartmann sensor is no longer an ideal wavefront gradient sensor when these real-world effects are taken into account.
		Atmospheric dispersion compensation is only required one band at a time, not for all bands simultaneously.
		Owing to the large beam sizes of 500 mm, the atmospheric dispersion correctors are uncommonly large, precluding the use of certain favored materials such as calcium fluoride.
	www.aura-nio.noao.edu /book/ch4/4_6_2.html (6716 words)

	Dainis Dravins (Lund Observatory)
		Atmospheric intensity scintillation of stars on milli- and microsecond time scales was extensively measured at the astronomical observatory on La Palma (Canary Islands).
		Scintillation at different wavelengths is not simultaneous: atmospheric chromatic dispersion stretches the atmospherically induced "flying shadows" into "flying spectra" on the ground.
		The effect is due to atmospheric dispersion, which stretches the "flying shadows" into "flying spectra" on the ground.
	www.astro.lu.se /~dainis/HTML/COLOR.html (795 words)

	Space Power By Ground-based Laser Illumination (Site not responding. Last check: 2007-10-24)
		Atmospheric turbulence limits the resolution limit of astronomical telescopes to slightly less than 1 second of arc, or about 4 microradians, increasing slightly at shorter wavelengths.
		The ability to compensate atmospheric turbulence rapidly degrades as the pathlength through the atmosphere increases, and it is likely that the maximum angle from zenith for which the system can be used will be in the range of 45° to 60°.
		A high power free electron laser operating at ten microns is currently under construction and should be operational by 1995; this laser is capable of being adapted to operation in the desired range of about 850 nm, where typical photovoltaic cells operate.
	powerweb.grc.nasa.gov /pvsee/publications/lasers/laser_IECEC.html (2476 words)

	Coronas
		The diffraction by a tiny opaque barrier shows the same pattern as that of an aperture of the same size and shape in an otherwise opaque screen (Babinet's principle).
		The phenomenon is one of diffraction, with smaller droplets giving larger glories, and Mie scattering is thought to be the mechanism controlling the intensity of light scattered back to the viewer.
		When the same diffraction effects occur in clouds some distance from the sun which are composed of tiny uniform droplets, colorful bands or "iridescence" can be seen.
	hyperphysics.phy-astr.gsu.edu /hbase/atmos/corona.html (552 words)

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