Review

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Review
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The Wave Nature of Light
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Important When a light wave travels from one
medium to another, its frequency does not change,
but its wavelength does.
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• Why we do not notice any dispersion when light
  passes through a windowpane?

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• What does the dispersion of light tell us about
  the speeds of various colors of light in a
  material?
• Will the converging lens focus blue light or red
  light at a closer distance to the lens? Explain.

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Interference Youngs Double Slit Experiment
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Constructive Interference
Destructive Interference
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• Would yellow light or green light produce the
  wider two-slit interference pattern?
• If light and sound are both wave phenomena, why
  can we hear sounds around a corner but cannot see
  around a corner?
• Red light is used to form a two-slit interference
  pattern on a screen. As the two slits are moved
  farther apart, does the separation of the bright
  bands on the screen decrease, increase, or remain
  the same?

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Diffraction by a Disk
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Diffraction by a Single Slit
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Limits of Resolution
The ability of lens to produce distinct images of
two point objects very close together is called
the resolution of lens.
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• Why cant an ordinary microscope using visible
  light be used to observe individual molecules?
• Is it better to use red light or blue light to
  minimize diffraction effects while photographing
  tiny objects through a microscope? Why?
• Why are the diffraction effects of your eyes more
  important during the day than at night?

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Interference by Thin Film
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A beam of light reflected by a material whose
index of refraction is greater than that of the
material in which it is traveling, changes phase
by ½ cycle.
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Polarization
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• Can sound waves be polarized?

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Early Quantum Theory and Models of the Atom
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Discovery of Electron
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Rutherfords Model
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Blackbody Radiation
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A blackbody is a body that would absorb all the
radiation falling on it.
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Plancks Quantum Hypothesis
Plancks assumption suggests that the energy of
any molecular vibration could be only some whole
number multiple of hf
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• If all objects emit radiation, why dont we see
  most of them in the dark?
• Rutherfords model provided an explanation for
  the emission of light from atoms. What was this
  mechanism and why was it unsatisfactory?
• Suppose you were a nineteenth-century scientist
  who had just discovered a new phenomenon known as
  Zeta rays. What experiment could you perform to
  define if Zeta rays are charged particles or e/m
  waves? Could this experiment distinguish between
  neutral particles and an e/m wave?

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The Photoelectric Effect
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• An increase in intensity of the light beam means
  more photons are incident, so more electrons will
  be ejected , but max KE in not changed.
• If the frequency of the light is increased, the
  max KE increases linearly.
• If the frequency f is less than the cutoff
  frequency f0, no electrons will be ejected at
  all, no matter how big is the intensity.

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• If a metal surface is illuminated by light at a
  single frequency, why dont all the
  photoelectrons have the same kinetic energy when
  they leave the metals surface?
• What property of the emitted electrons depends on
  the intensity of incident light?
• What property of the emitted photoelectrons
  depends on the frequency of incident light?

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Bohrs Model
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Allowed Angular Momenta
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Bohrs Second Postulate
An electron doesnt radiate when it is in one of
the allowed orbits.
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Bohrs Third Postulate
A single photon is emitted whenever an electron
jumps down from one orbit to another.
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• Why do astronomers often use the terms color and
  temperature interchangeably when referring to
  stars?
• Why did Bohr assume that the electrons do not
  radiate when they are in the allowed orbits?

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Wave Nature of Matter
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De Broglie Wavelength
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The Heisenberg Uncertainty Principle
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• Why do astronomers often use the terms color and
  temperature interchangeably when referring to
  stars?
• Why did Bohr assume that the electrons do not
  radiate when they are in the allowed orbits?

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Wave Nature of Matter
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De Broglie Wavelength
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The Heisenberg Uncertainty Principle
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Particle in a Box
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Quantum Mechanics of the Hydrogen Atom
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n principal quantum number, positive integer l
orbital quantum number, is related to the
magnitude of the angular momentum of the
electron at given n can take integer values from
0 to (n-1) ml magnetic quantum number, is
related to the direction of the electrons
angular momentum, and it can take an integer
values from l to l.
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Selection Rule
Another prediction of quantum mechanics is that
when a photon is emitted or absorbed, transitions
can occur only between states with values of l
that differ by one unit.
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The Exclusion Principle
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No two electrons in an atom can occupy the same
quantum state.
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• How many electrons have the quantum numbers n5
  and l1?
• How many electrons can have the quantum numbers
  n5 and l4?
• Why do some minerals glow when they are
  illuminated with ultraviolet light?

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Radioactivity
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Alpha Decay
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Transmutation
parent daughter
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Beta Decay
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Gamma Decay
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• Which of the three types of radiation will
  interact with electric field?
• Why do beta rays and alpha rays deflect in
  opposite directions when moving through a
  magnetic field?

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• What happens to the charge of the nucleus when it
  decays via beta plus decay?
• What happens to the charge of the nucleus when it
  decays via electron capture?
• What changes in the numbers of neutrons and
  protons occur when a nucleus is bombarded with a
  deuteron (containing one neutron and one proton)
  and an alpha particle is emitted?

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Half-Life and Rate of Decay
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• You place a chunk of radioactive material on a
  scale and find that it has a mass of 4 kilogram.
  The half-life of the material is 10 days. What
  will the scale read after 10 days?
• A radioactive material has a half-life of 50
  days. How long would you have to watch a
  particular nucleus before would see it decay?