CBSE Class 11-science Answered
every object have dual character....explain!!
Asked by | 12 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
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
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 | 12 May, 2008, 06:30: PM
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