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Unformatted text preview: 1 PHYS132 FALL2010 Instructor : A. Meenakshi Ph.D. Email: [email protected] Office: Science II, Room 154 Office Hours: Tues Friday 10:00 am 11:15 am 2 Topics: • Light and Optics • The Interference of Light (due to wave front division) • The Diffraction Grating • SingleSlit Diffraction • CircularAperture Diffraction • Interferometers (Amplitude Division) Chapter 22. Wave Optics 3 Chapter 22 Wave Optics • Understand light’s characteristics wave, particle, and particle and wave; • Phenomena where each of these nature manifests show me the evidence! • Wave nature Calculate interference due to double slits, and multiple slits (a.k.a. diffraction gratings) • Huygens' Principle • Understand diffraction pattern (single slit, circular aperture and circular disk …), Resolution • Interference Amplitude division Michelson’s interferometer. 4 Models of Light • The wave model: under many circumstances, light exhibits the same behavior as sound or water waves. The study of light as a wave is called wave optics . • The ray model: The properties of prisms, mirrors, and lenses are best understood in terms of light rays . The ray model is the basis of ray optics . • The photon model: In the quantum world, light behaves like neither a wave nor a particle. Instead, light consists of photons that have both wavelike and particlelike properties. This is the quantum theory of light. 5 6 Interference – Young’s DoubleSlit Experiment If light is a wave, interference effects will be seen, where one part of wavefront can interact with another part. One way to study this is to do a doubleslit experiment: 7 Interference of Light – Young’s DoubleSlit Experiment If light is a wave, interference effects will be seen, where one part of wavefront can interact with another part. Conditions for interference: (a)The sources must be coherent. i.e. they should have constant phase difference and (b) have the exact same wavelength (monochromatic). The coherence conditions are hard to attain with natural sources; So, we use a single source and split the output to produce interference. wavefront division; 8 9 10 From last chapter: Constructive interference: r = m where m=0, 1, 2, 3,... (1) From the figure: r = dsin Thus, we get bright fringes (constructive interference) if r = dsin m m λ θ θ λ ∆ ∆ ∆ = 11 Analyzing DoubleSlit Interference The m th bright fringe emerging from the double slit is at an angle where θ m is in radians, and we have used the smallangle approximation. The yposition on the screen of the m th fringe is while dark fringes are located at positions Snapshot of Interference 12 13 Locating fringes example: • A double slit system is illuminated by a light source of...
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 Spring '08
 Pompi
 Diffraction, Light, Wavelength, Thomas Young, Double Slit

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