every object have dual character....explain!!

Asked by  | 12th May, 2008, 10:52: AM

Expert Answer:

Newton's Corpuscular Theory of Light (1670)
  • light corpuscles have mass and travel at extremely high speeds in straight lines
  • rectilinear propagation - blocked by large objects (well-defined shadows)
  • obey the law of reflection when bounced off a surface
  • speed up when they enter denser media (gravitational force of attraction, net F = ma)
  • paths in denser media "bend towards the normal"
  • prism dispersion - contradicted corpuscular theory
  • mathematical theory - the speed he predicted for electromagnetic waves nearly matched the measured speed of light leading him to predict that light was an electromagnetic wave
  • Maxwell's predicted speed (c = squareroot (1/µoepsilono) was verified by Heinrich Hertz in 1888 by timing the sparks between two induction coils and calculating the ratio of distance/time
    Photoelectric effect (1905)
    • light is made of photons
    • quantized packets of radiant energy
    • one photon emits one photo-electron
    • current is proportional to the intensity of the light
    • KE of the emitted photo-electrons is proportional to the frequency of the light

    Compton Effect (1923) - bombarded graphite crystals with x-rays
    • electrons were released - the momentum of the electrons revealed their KE which matched the energy lost by the x-rays - a classic collision had occured in which momentum was conserved
    • x-rays have momentum

    from special relativity E = mc2
    momentum (p) = mv = (E/c2)(v)
    for light, v = c
    therefore p = E/c
    since E = hf = h(c/λ),
    p = (hc/λ)/c
    p = h/λ
    • photons (quantized bundles of radiant energy) which have no mass do have momentum!
    Wave Nature of Particles 
    deBroglie wavelength (1923)
    • λdeBroglie = h/mv
    • an integer multiple of an electron's deBroglie wavelength produced a steady state orbital

    Davisson-Germer Experiment (1927)
    • diffraction of electrons through a crystal revealed the same pattern as x-rays diffracted through the crystal
    • high energy electrons have wavelengths
    • electron microscopes
  • Answered by  | 12th May, 2008, 06:30: PM

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