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Lecture 38

Lecture 38. Radiation Energy Density. EM Wave:. Equal partitions:. Intensity:. Time dependence of I at x = x 0 :. Time averaged value:. Intensity Vector (Poynting Vector). Show that:. Energy-Momentum Relationship: Relativistic Kinematic. For a particle will mass m :.

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Lecture 38

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  1. Lecture 38 Radiation Energy Density EM Wave: Equal partitions: Intensity:

  2. Time dependence of I at x = x0: Time averaged value:

  3. Intensity Vector (Poynting Vector) Show that: Energy-Momentum Relationship: Relativistic Kinematic For a particle will mass m: Light particle: photon

  4. Radiation Pressure Geometry Dependent A: Reflective Example Geometric consideration: Light beam shining on a book: Bulb shining on a book:

  5. Polarization Define: Direction of polarization = direction of oscillation of E Metal perpendicular strips: E-parallel drives electron oscillation Large induced current Energy absorbed by medium E-perp. Negligible induced current This component can be transmitted The strip setup serves as a polarizer. If the incident light is unpolarized (i.e. polarization is uniformly distributed in the azimuthal direction) the outgoing light will be polarized in the vertical direction – direction of E-parallel If the incident light is polarized along E where there is angle θ between E-perp and E, then E-perp = E cosθ, Outgoing Intensity: This is Malus’ law.

  6. Metal Strip Analyzer • Rotating the strip can check polarization of the incident light. • Unpolarized incident light, if no variation in intensity • Unpolarized light may be represented by two equal weight mutually perpendicular polarized lights • Two mutually perpendicular analogues can fully block out an polarized light Radiation from a charged particle initially at rest: Direction of magnetic force on q initially at rest: HINT: Notice:

  7. The polarized sky light Sunlight: Unpolarized light Rescattered light observed by ground observer is polarized along z Fig(mi) 24.51 Intensity of scattered light: Compare Intensity of rescattered light with frequencies ω1 and ω2:

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