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Classical Physics
Newtons laws:
allow prediction of precise trajectoryfor particles, with precise locations andprecise energy at every instant.
allow translational, rotational, andvibrational modes of motion to beexcited to any energy by controllingapplied forces.
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Wavelength(l) - distance between identical points onsuccessive waves.
Ampl i tude- vertical distance from the midline of a
wave to the peak or trough.
Fig 8.1 Characteristics of electromagnetic waves
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Properties of Waves
Frequency(n) - the number of waves that pass through aparticular point in 1 second (Hz = 1 cycle/s).
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Maxwell (1873) proposed that visible light consists
of electromagnetic waves.
Electromagnet ic
radiat ion- emission and
transmission of energy in
the form of
electromagnetic waves.
Speed of light (c) in vacuum = 3.00 x 108 m/s
All electromagnetic
radiation:
c
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Figure 8.2 The Electromagnetic Spectrum
R O Y G B I V
c
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Mysteries of classical
physics
Phenomena that cant be explained
classically:
1. Blackbody radiation
2. Atomic and molecular spectra3. Photoelectric effect
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Fig 8.4 Experimental representationof a black-body
Capable of absorbing & emitting all frequencies uniformly
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Fig 8.3
The energy distribution in a
black-body cavity at several
temperatures
Stefan-Boltzmann law:
E = aT4E
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Fig 8.5
The electromagnetic vacuum
supports oscillations of the
electromagnetic field.
Rayleigh -
For each oscillator:
E = kT
Rayleigh
Jeans law:
dE = d
where: 4
kT8
l
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Fig 8.6
Rayleigh-Jeans predicts
infinite energy density atshort wavelengths:
ll
dkT84
dE =
Ultraviolet catastrophe
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Fig 8.7
The Planck distribution
accounts for experimentallydetermined distribution ofradiation.
dE = d
]1
kT
hc[exp
hc8
5
l
Planck: Energies of the
oscillators are quantized.
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Fig 8.10 Typical atomic spectrum:
Portion of emission
spectrum of iron
Most compelling evidencefor quantization of energy
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Fig 8.11 Typical molecular spectrum:
Portion of absorption
spectrum of SO2
Contributions from:
Electronic,
Vibrational,
Rotational, and
Translational excitations
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E = hE = hc/
Fig 8.12 Quantized energy levels
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Light has both:
1. wave nature
2. particle nature
hn = KE +
Photoelectric Effect
Photonis a particle of light
KE = hn
hn
KE e-
Solved by Einstein in 1905
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Fig 8.13 Threshold work functions for metals
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Fig 8.14 Explanation of photoelectric effect
For photons: E
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Fig 8.15 Davisson-Germer experiment
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Fig 8.16 The de Broglie relationship
ph
mvh
Wave-Particle Duality
for:
Light andMatter