Review for exam 4

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Review for exam 4

• As with all other powerpoint exam reviews for
  this course, this is not a complete review
• It consists only of a collection of slides I was
  able to find and adapt for this purpose.
• There are topics covered in your homework (and
  which may therefore appear on an exam) that are
  not included in this review.

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Chap 17Sections 1-4Light and Image Formation
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Reflection Image Formation by a Plane Mirror
Law of reflection the angle of reflection (that
the ray makes with the normal to a surface)
equals the angle of incidence.
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Reflection Image Formation by a Plane Mirror
What you see when you look into a plane (flat)
mirror is an image, which appears to be behind
the mirror.
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Reflection Image Formation by a Plane Mirror
This is called a virtual image, as the light does
not go through it. For a plane mirror, the
distance of the image from the mirror is equal to
the distance of the object from the mirror.
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Formation of Images by Curved Mirrors
Curved mirrors may be reflective on either the
inside (concave) or outside (convex).
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Index of Refraction
In general, light slows somewhat when traveling
through a medium. The index of refraction of the
medium is the ratio of the speed of light in
vacuum to the speed of light in the medium
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Refraction Snells Law
Refraction is what makes objects half-submerged
in water look odd.
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Refraction Snells Law
Light changes direction when crossing a boundary
from one medium to another. This is called
refraction, and the angle the outgoing ray makes
with the normal is called the angle of refraction.
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Law of refraction (Snells law)
For small angles
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Thin Lenses Ray Tracing
Parallel rays are brought to a focus by a
converging lens (one that is thicker in the
center than it is at the edge).
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Thin Lenses Ray Tracing
A diverging lens (thicker at the edge than in the
center) make parallel light diverge the focal
point is that point where the diverging rays
would converge if projected back.
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Thin Lenses Ray Tracing
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Thin Lenses Ray Tracing
For a diverging lens, we can use the same three
rays the image is upright and virtual.
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The Thin Lens Equation
The distances i from the lens to the image o
from the lens to the object f the focal length
of lens Are related by the lens equation
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Chap 18The atom
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Plancks Quantum Hypothesis Blackbody Radiation
Max Planck in 1900 The energy of atomic
oscillations within atoms cannot have an
arbitrary value it is related to the frequency
The constant h is now called Plancks constant.
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Plancks Quantum Hypothesis Blackbody Radiation
Planck found the value of his constant
Plancks proposal was that the energy of an
oscillation had to be an integral multiple of hf.
This is called the quantization of energy.
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Early Models of the Atom
It was known that atoms were electrically
neutral, but that they could become charged,
implying that there were positive and negative
charges and that some of them could be removed.
One popular atomic model was the plum-pudding
model
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Early Models of the Atom
The plum-pudding model had the atom consisting of
a bulk positive charge, with negative electrons
buried throughout.
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Early Models of the Atom
Rutherford did an experiment that showed that the
positively charged nucleus must be extremely
small compared to the rest of the atom. He
scattered alpha particles helium nuclei from
a metal foil and observed the scattering angle.
He found that some of the angles were far larger
than the plum-pudding model would allow.
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Early Models of the Atom
The only way to account for the large angles was
to assume that all the positive charge was
contained within a tiny volume now we know
that the radius of the nucleus is 1/10000 that of
the atom.
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Early Models of the Atom
Therefore, Rutherfords model of the atom is
mostly empty space
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The Bohr Atom
Bohr proposed that the possible energy states for
atomic electrons were quantized only certain
values were possible. Then the spectrum could be
explained as transitions from one level to
another.
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Chap 19The nucleus and nuclear energy
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Nuclear Reactions
A nuclear reaction takes place when a nucleus is
struck by another nucleus or particle. An
example
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Nuclear Fission
After absorbing a neutron, a uranium-235 nucleus
will split into two roughly equal parts. One way
to visualize this is to view the nucleus as a
kind of liquid drop.
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Nuclear Fission
The energy release in a fission reaction is quite
large. Also, since smaller nuclei are stable with
fewer neutrons, several neutrons emerge from each
fission as well.
These neutrons can be used to induce fission in
other nuclei, causing a chain reaction.
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Nuclear Fission Nuclear Reactors
In order to make a nuclear reactor, the chain
reaction needs to be self-sustaining it will
continue indefinitely but controlled.
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Nuclear Fission Nuclear Reactors
Neutrons that escape from the uranium do not
contribute to fission. There is a critical mass
below which a chain reaction will not occur
because too many neutrons escape.
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Nuclear Fusion
The lightest nuclei can fuse to form heavier
nuclei, releasing energy in the process. An
example is the sequence of fusion processes that
change hydrogen into helium in the Sun. They are
listed here
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Chap 20Sections 1-3Special Relativity
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Relativity

• Definition of an inertial reference frame
• One in which Newtons first law is valid
• Earth is rotating and therefore not an inertial
  reference frame, but can treat it as one for many
  purposes
• A frame moving with a constant velocity with
  respect to an inertial reference frame is itself
  inertial

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Relativity
Relativity principle The basic laws of physics
are the same in all inertial reference frames.
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Einsteins Postulates of the Special Relativity

• The laws of physics have the same form in all
  inertial reference frames.
• Light propagates through empty space with speed
  c independent of the speed of source or observer.
  In other words, the speed of light is the same in
  all inertial reference frames.

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Simultaneity
One of the implications of relativity theory is
that time is not absolute. Distant observers do
not necessarily agree on time intervals between
events, or on whether they are simultaneous or
not. In relativity, an event is defined as
occurring at a specific place and time.
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Time Dilation
A different thought experiment, using a clock
consisting of a light beam and mirrors, shows
that moving observers must disagree on the
passage of time.
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Chap 21Sections 1-3Quarks Cosmology
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Elementary Particle Physics
the four known forces
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Particles and Antiparticles
The positron is the same as the electron, except
for having opposite charge. We call the positron
the antiparticle of the electron.
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Quarks
Here are the quark compositions for some baryons
and mesons
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Quarks
This table gives the properties of the six known
quarks.