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Quantum Theory, With Atomic and
Nuclear Physics.
History of Atomic Models (I)
1. Single indivisible particle,
“atomos” Greek.
Democritus(460-370 BC)
2. Plum Pudding Model
J.J. Thomson(1856-1940),
England, used his CRT to
discover the electron.
Some Early Apparatus
Thomson’s CRT (photo)
Schematic Drawing
Question: What
does CRT stand for?
Cathode Ray Tube
Robert Millikan (1868-1953) and his
Oil-Drop Experiment in 1909.
Proved that the elementary unit of charge, 1.6x10-19 C
only occurred in certain amounts (Quantized).
History of Atomic Models (II)
3. Planetary Model - imagine the
solar system with the Sun as the
nucleus and the planets as the
electrons.
Ernest Rutherford(1871-1937),
England, Gold-foil Experiment.
Results:
(1) most of the atom is empty space
(2) almost all the mass is in the
nucleus.
The Rutherford Scattering(Gold Foil) Experiment
Contributors to the Photoelectric Effect
and
Quantum Theory
Heinrich Hertz
Max Planck
Albert Einstein
1857-1894
1858-1947
1879-1955
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The Photoelectric Effect
 Discovered for the first time by Max Planck and Heinrich Hertz,
Germany, in the late 1800’s.
• Light is sent to a metal surface.
• If the frequency of the light is
high enough, the light kicks
electrons off the surface of the
metal.
• Emitter is connected to the
negative terminal of a battery.
• Collector is attached to the
positive terminal.
• Result: The Photocell.
Carbon Arc Light
Photoelectric
effect
Einstein put forward a theory:
• Light energy is quantized.
• Light consists of a stream of particles
called photons.
• The energy of each photon (E) depends
on the frequency (f ) of the light.
Frequency increasing
ONE
PHOTON
GIVES ALL ITS ENERGY
e
TO ONE ELECTRON
The Explanation of
the Photoelectric Effect
The emission of electrons from a material that is
bombarded with radiation in the form of light.
Ephoton = hf
with h = 6.6 x 10-34 J ·s
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Problem #1. Calculate the energy of a photon of
light having a frequency of 2.5x1015 Hz.
(Show your work.)
Given: f = 2.5x1015 Hz
We know Planck’s Constant.
h = 6.6x10-34 Js
Equation: E = hf
E = ___________
Solution:
E = 6.6x10-34 Js · 2.5x1015 Hz
E = 1.7x10-18 J
All parts of the Electromagnetic Spectrum move at the same
speed through a vacuum: 3.0 x 108 m/s.
We call this the speed of light and assign it the letter, c .
But all possess the 5 properties of waves, so they must obey
the wave equation, c = f·λ .
The energy is carried by mass-less photons, and computed
with the equation, E = h•f . ( h = 6.6 x 10-34 Js )
Summary of the Equations for
Photoelectric Effect and Quantum Theory
Energy of a photon of light
E = h·f
h = 6.6 x 10-34 J ·s
c = f ·
Wave equation for light, c = 3.0 x 108 m/s
Wo = h·fo
Work function, with fo = threshold frequency
KEmax = q·Vo
KEmax = E - Wo
E=
mc2
Maximum kinetic energy of photoelectrons
based on stopping potential, Vo
Maximum kinetic energy of photoelectrons
based on photon energy and work function
Einstein’s equation for conversion of
matter to energy
Combine these three equations to get a single
equation for the wavelength of a matter particle.
E = mc2
c = f ·
E = h·f
The equation is:  = h / (mv)
“If waves (light) can act like
particles, why can’t particles act
like waves”.
Prince Louis Victor deBroglie
(1892-1987), France.
Matching Exercise.
• Found charge on electron
with Oil-drop experiment
• J. J. Thomson
• Unit of frequency named
after him
• Ernest Rutherford
• Made the first CRT
• Robert Millikan
• Gave us the equation E = mc2
• Atom is single indivisible
• Max Planck
particle
• Heinrich Hertz
• Planetary atomic model
-34 Js
•
His
constant
is
6.6x10
• Albert Einstein
• Democritus
Can you then come-up with the equation for
the momentum of a photon? Remember, if
particles can act like waves, why can’t waves
act like particles?
The equation is: p = h / 
Useful constants: 1 eV = 1.6 x 10-19 J
mass of electron = 9.11 x 10-31 kg
mass of proton = 1.67 x 10-27 kg
charge on the electron = -1.6 x 10-19 C
charge on the proton = 1.6 x 10-19 C
Problem #2. Calculate the threshold frequency of
a metal having a work function of 6.4 eV.
(Show your work.)
Given: Wo = 6.4 eV
We know Planck’s Constant.
h = 6.6x10-34 Js
Equation: Wo = hfo
fo = ___________
Solution:
fo = Wo / h
= (6.4 eV x 1.6 x 10-19 J / 1 eV) / 6.6x10-34 Js
fo = 1.6x1015 Hz
Problem #3. A metal has a threshold frequency of 3.3
x 1014 Hz. Light with a frequency of 2.0 x 1015 Hz
shines on the metal. Find the maximum kinetic energy
of the photoelectrons. (Show your work.)
Given: fo = 3.3x1014 Hz
f = 2.0x1015 Hz
Planck’s Constant, h = 6.6x10-34 Js
KEmax = ___________
Equation: KEmax = hf – hfo = h(f – fo )
KEmax = 6.6x10-34 Js(2.0x1015 Hz – 3.3x1014 Hz )
KEmax = 1.1x10-18 J
Problem #4. Calculate the de Broglie wavelength of a
cannon ball with a mass of 100.0 g and a velocity of
7.0x102 m/s. (Show your work.)
Given: m = 100.0 g = .1000 kg
v = 7.0x102 m/s
Equation: λ = h/mv
λ = ___________
h = 6.6x10-34 Js
Solution: λ = 6.6x10-34 Js / (.1000 kg ·7.0x102 m/s)
λ = 9.4x10-36 m
History of Atomic Models (III)
4. Planetary-Quantum model was
proposed to align atomic theory with
the new physics of Quantum Theory.
Niels Bohr(1885-1962), Denmark, determined
the equations for rn = 5.3 x 10-11 m x n2 and
En = -13.6 eV x 1/n2
The Bohr Model - Planetary Quantum
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The Discovery of Radioactivity
ALPHA
BETA
GAMMA
Henri Becquerel
(1852-1908)
Nuclear Physics.
Nuclear Physics.
X-Ray Production by
Wilhelm Röntgen (1895)
The Geiger-Muller Tube (Geiger Counter). demo
Contributors to the Study of Nuclear Physics
The Nobel Prize in Physics 1903
"in recognition of the extraordinary
services they have rendered by their
joint researches on the radiation
phenomena discovered by Professor
Henri Becquerel"
Pierre Curie
France
1/4 of the prize
Marie Curie, née Sklodowska France
1/4 of the prize
This is …
"in recognition of the
extraordinary services he
has rendered by his
discovery of spontaneous
radioactivity"
Antoine Henri Becquerel
1/2 of the prize (France)