Phys2212_22.1+to+22.6

Phys2212_22.1+to+22.6 - Physics 2212 Waves Lecture 3 Wave...

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Unformatted text preview: Physics 2212 Waves Lecture 3 Wave Optics 06/08/09 Physics 2212 - Lecture 3 2 Crossed Polarizers The direction of polarization after transmission through a series of polarization filters always matches the pass direction of the last filter. 06/08/09 Physics 2212 - Lecture 3 3 Maluss Law A polarizing filter blocks the component of light that has the plane of polarization in a particular direction, i.e., it absorbs and blocks that component of the E field. Unpolarized light passed through such a filter emerges polarized in the pass direction, with about the intensity of the incident beam. If such a polarized wave now is passed through a second polarizing filter, the intensity of the transmitted wave depends of the angle between the filter pass direction and the incident plane of polarization. The relation for intensity is called Maluss Law: incident sin cos E E i E j E i E j P r transmitted cos E E j E j P r 2 transmitted cos I I 06/08/09 Physics 2212 - Lecture 3 4 Models of Light Is light a particle or a wave? Physics in the 20 th century has shown that this simple question does not have a simple answer. The behavior of light, depending on the circumstances, can be described by three distinct (and seemingly contradictory) models. We will introduce all of them and learn the conditions and circumstances under which each is valid. The Wave Model: This model works in many circumstances. When it is applicable, light shows the same interference behavior as water waves and sound waves. Lasers and electro-optical devices, critical technologies of the 21 st century, are best understood with the wave model of light, which we will call wave optics. The Photon Model: This model works in circumstances where energy detection is important, as describes light as a stream of photons, particles that carry packets of energy called quanta . The Ray Model: Light travels in straight lines, modified by reflection and refraction. This model works best for optical instruments and lenses, and is the basis for ray optics . 06/08/09 Physics 2212 - Lecture 3 5 Light Through One Slit When light passes through a narrow slit, it spreads out in a way that is inconsistent with ray optics. If light consisted of corpuscles traveling in straight lines, as Newton thought, it should produce a narrow illuminated strip on the screen, rather than the broad pattern actually observed. Water waves moving through an aperture will show similar behavior. This is evidence of the wave properties of light. Newton lacked the technology to do such experiments, and so focused on the particle properties of light, anticipating 20 th century physics in the 17 th century. 06/08/09 Physics 2212 - Lecture 3 6 Youngs Experiment Thomas Young (1773-1829) In 1801, Thomas Young devised and performed an experiment demonstrating the wave nature of light. The difficulty confronting Young was that the usual light sources of the day (candles, lanterns, etc.) could not serve as coherent light sources of the day (candles, lanterns, etc....
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This note was uploaded on 06/07/2009 for the course PHYSICS 2212 taught by Professor Geist during the Fall '09 term at Georgia Perimeter.

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Phys2212_22.1+to+22.6 - Physics 2212 Waves Lecture 3 Wave...

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