Light Scattering

Light Scattering - Wave-particle duality Bundles or packets...

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Unformatted text preview: Wave-particle duality Bundles or packets of energy traveling traveling as electromagnetic waves Narrow band of the electromagnetic spectrum that we we “see” Backward scattering from a beam of light at an interface Excited and re-excited photons Angle of incidence =Angle of reflection reflection Most important application of total total internal reflection Propagation along fiber Light Communications Medicine Bending of light as it passes from one one medium to another with different densities Higher density – toward normal Lower density – away from normal Emerges parallel to to incident beam Bending of light as it passes around objects that have the same wavelength as the wavelength light itself Waves interfere with one another constructively or constructively destructively Sunlight refracted and reflected from a water droplet to create a spectrum of color Visible for a 40-42° angle of reflection Moving particles of light forced to deviate from a straight trajectory by one or more localized uniformities in the or medium Absorption and prompt re-emission of electromagnetic radiant energy by atoms and and molecules Single and multiple Particles, bubbles, droplets, bubbles droplets density fluctuations, crystalline defects, surface ll roughness, cells in organisms, fibers in clothing… T yndall effect 1871 – Lord Rayleigh Elastic scattering of electromagnetic radiation by particles smaller smaller than a wavelength of incident light Proportional to inverse fourth of inverse wavelength Responsible for: Blue sky Blue eyes Blue jay’s feathers Red sunset Scattering of electromagnetic radiation by particles larger than a wavelength of incident light Scatters most wavelengths Clouds and fog Crepuscular rays – bright light beams due to mie scattering by haze and dust due Applies to spheroids and ellipsoids Halo effect – ring of light extending ring from sun or moon; created as light is refracted refracted through ice crystals Inelastic scattering of an incident optical wave field between light and media, media, with thermally excited elastic waves in a sample Light interaction with phonons, magnons, or other quasiparticles Light changes its frequency and path 1912 – Sir William Bragg – confirmed existence existence of atomic particles Diffraction phenomenon exhibited by a crystal bombarded with x-rays; each s; plane of the crystal acts as a reflector Inelastic photon interaction with molecules molecules so the photons are shifted in frequency in vibrational modes Raman spectroscopy Air pollution detection Scattering of photons from charged particles through interaction with matter, resulting in lower energy and matter, longer wavelength Compton shift Uses Rayleigh scattering with chromatography chromatography to find molecular mass Light scattering reading proportional to to mass x concentration Proteins, monomers, nucleic acids Uses Zimm plot Scattered light intensities measured at at different angles Photon Correlation Spectroscopy uses uses scattered light to measure the rate of diffusion of protein particles Proteins, monomers, oligomers monomers oligomers Light reflects, refracts, diffracts, refracts diffracts and scatters in numerous ways…all around us! Light scattering has many applications in in scientific research Hecht, Eugene. Physics: Algebra/Trig Eugene ...
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