Transcript 2 Timeline of Quantum Theory

Quantum History
Columbus discovers
America
Pasteurization
1492
Max Planck
1861
Ford “Model A”
1900
Albert Einstein
Niels Bohr
1903
1905
WWI
1913-1915
Arthur Compton
1914 – 1919
Louis de Broglie
Werner Heisenberg
Erwin Schrodinger
1926
1922
1924
1925
WWII
Polio Vaccine
1939 – 1945
1st American
in Space
1952
1962
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Quantum History
Max Planck
Born April 23, 1858 - Died Oct. 3, 1947
• German physicist
• Referred to as the father of quantum physics
• Was awarded the Nobel Prize in 1918
for his discovery of energy quanta
1900 - Planck hypothesized that there is a minimum size
in which atoms can release or absorb energy.
He showed that energies must be quantized to explain the
spectrum of radiation emitted from certain objects.
The energy values are
restricted to whole
number quantities of hv.
E  h f
2
Planck’s constant
6.63 x 10-34 J.s
Frequency (s-1)
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Quantum History
Albert Einstein
• Born March 14, 1879 - Died April 18, 1955
• German physicist
• Awarded the Nobel Prize in Physics in
1921 for his discovery of the photoelectric
effect
1905 - Einstein used Planck’s quantum theory to explain
the photoelectric effect.
• Every metal has a minimum frequency of light for
which it will emit electrons.
He hypothesized that the light striking the surface of the metal
is a stream of tiny energy particles he called photons.
E photon  h  f
The energy of each photon
must be proportional to the
frequency of the light.
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Niels Bohr
• Born Oct. 7, 1885 - Died Nov. 18, 1962
• Danish physicist
• Awarded the Nobel Prize in Physics in 1922
for his investigation of atomic structure and
the radiation they emanate
1913 - Bohr developed a model of the hydrogen atom
that explains its emission line spectrum.
Bohr borrowed Planck’s idea that energies are quantized
and proposed that only orbits of certain radii corresponding
to defined energies are permitted.
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• Bohr assumed that electrons could “quantum jump” from
one allowed orbit to another by absorbing or emitting
photons of light with specific frequencies.
• A photon is absorbed when an electron moves to an
orbit with a higher energy state and is emitted when an
electron moves to an orbit with a lower energy state.
• Bohr’s model states that only photons of specific frequencies
can be absorbed or emitted by the atom.
these frequencies must correspond to the energy
difference between two orbits.
• Bohr’s model was important because it introduced the
idea of using quantized energy stated for electrons in
atoms. However, his model is only accurate for atoms or
ions with a single electron.
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Arthur H. Compton
• Born Sept. 10, 1892 - Died March 15, 1962
• American physicist
• Awarded the Nobel Prize in Physics in
1927 for his discovery of the Compton Effect
1922 - Discovered that the wavelength of x-rays would
increase when they are collided with and scattered by free
electrons in matter.
- This increase in wavelength means that the x-ray photons
can transfer quanta of energy to the electron upon collision.
This was a strong verification for quantum theory because
explanation of the effect required that the x-rays be
looked at as particles rather than as waves.
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Louis de Broglie
• Born Aug. 15, 1892 - Died Mar. 19, 1987
• French physicist
• Awarded the Nobel Prize in Physics in 1929
for his discovery of the wave nature of
electrons.
1924 - De Broglie proposed that an electron in its orbit around
the nucleus has a particular wavelength associated with it.
The wavelength of any particle
is dependent on its mass and
velocity.
h

mv
Planck’s constant
6.63 x 10-34 J.s
Mass (kg)
Velocity (m/s)
1927 - Wave nature of the electron was experimentally
proven using electron diffraction by Davisson and Germer.
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Werner Heisenberg
• Born Dec. 5, 1901 - Died Feb 1, 1976
• German physicist
• Awarded the Nobel Prize in 1932 for the
creation of quantum mechanics.
1925 - Published his theory of quantum mechanics
• Formulated his new theory in terms of matrix equations.
1927 - Uncertainty Principle
• It is impossible to know both the exact momentum of
an electron and its exact location in space at the same
time.
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Erwin Schrodinger
• Born Aug. 12, 1887 - Died Jan. 4, 1961
• Austrian physicist
• Awarded a share of the Nobel Prize in
Physics in 1933 for the development of his
wave equation.
1926 - Wave Equation
• Schrodinger’s wave equation includes both the wave-like
and particle-like behavior of the electron.
• The square of the wave function represents the
probability that an electron will be in a certain place at a
given instant of time.
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