PHYSICS 1306
EXAM II
Form 1 Dr. Pinsky
Spring 2004
This is a CLOSED BOOK exam. You may use a calculator, however you
may not have any information stored in any user changeable memory prior to the
beginning of the exam for any calculator that you use. Keep your eyes on your own paper at all
times. THERE MAY BE MORE THAN ONE
CORRECT ANSWER PER QUESTION, OR THERE MAY BE NO CORRECT ANSWERS FOR A QUESTION. Mark all correct answers. Grading will be RIGHT MINUS WRONG (answer by answer, not question by question). DO NOT GUESS !
1. On
an HR diagram:
a. Écooler
stars are generally plotted lower on the diagram than hotter stars.
b. Éa lower
luminosity star can never be appear higher up anywhere on the HR diagram with
respect to the vertical axis than any star with a higher luminosity.
c. ...the
horizontal axis can be plotted as temperature.
d. ...the
vertical axis can be plotted in spectral types.
e. Éany star
that is generally both above and to the right of another star must always be the larger of the
two stars.
2. Concerning
stellar evolution:
a. All
stars less massive than the Sun generally evolve slower than the Sun as they
initially evolve towards the ZAMS.
b. T-Tauri
variables are generally thought to be examples of Pre-ZAMS phenomena.
c. all
hydrogen "burning" concludes in the central-most core in the starŐs
interior once a star leaves the main sequence.
d. all
observed variable stars are in a post main sequence phase.
e. stars are always
hotter at their surface when they "Helium Flash" than when they first
left the main sequence.
3. Along
the main sequence (for main sequence stars):
a. All stars
with a surface temperature substantially greater than the SunŐs have faster
rates of evolution.
b. All stars
with a surface temperature substantially less than the SunŐs have masses that
are less than the SunŐs as well.
c. All stars
are "burning" hydrogen in their central-most cores.
d. All stars with
a substantially greater luminosity than the SunŐs will have greater total main
sequence lifetimes as well.
e. The numbers
of main sequence stars are distributed roughly equally both above and below the
ZAMS (Zero Age Main Sequence) at each point along the main sequence.
4. Our
present theory of the Sun's internal structure is in some significant way based
on our knowledge of:
a. Éthe oldest
biological growth records on earth being used to determine the constancy of the
SunŐs luminosity over the largest part of itsŐ prior main sequence lifetime.
b. Éthe fact
that Jupiter has a composition thought to be identical to the Sun's.
c. Éthe length
of time it takes the Jupiter to orbit once around the sun to determine the
SunŐs angular momentum.
d. Éthe
spectrum of the light coming from the Sun to determine the details of the SunŐs
composition at its outer surface.
e. Éthe period
and semi-major axis of the earth's orbit to determine the SunŐs mass.
5. Neutron
stars:
a. Édo not collapse
further because electrons are fermions and they can become degenerate.
b. Éare
typically only about 10,000 miles across (~the size of the Earth).
c. are thought to be the explanation
for pulsars in many cases.
d. Éare all
thought to be remnants of supernovae.
e. Éall have
masses greater than the SunŐs.
6. Supernovae:
a. Éresult, at
least sometimes, in the formation of white dwarfs.
b. Érelease
most of their energy in the form of neutrinos.
c. Éfor a few
seconds, have a net luminosity that outshines the rest of the visible universe
combined.
d. Écan occur
for white dwarfs in a binary system when it gets mass dumped on it by a
companion star.
e. Éhave
progenitors which are always red giants (the star that becomes a supernova was
a red giant just before that) for both Type I and Type II Supernovae.
7. The
fundamental postulates of Special Relativity include or imply:
a. clocks
appear to run slower to an observer when the observer in question is fixed and
the clock is moving, but not when the clock is fixed and that the observer in
question is moving.
b. the laws of
physics do not depend upon the frame of the observer so long as it is an
inertial frame of reference.
c. distant
objects will appear to be closer to a person moving towards them than they do
to a person who is at rest with respect to the distant object and is being
passed at that moment by the moving observer..
d. light
appears to move at the same speed in a vacuum as measured by all observers who
are in inertial frames of reference.
e. information
can never be transmitted in the form of light.
8. For
Black Holes:
a. the phase
"Black holes have no hair" refers to the idea that black holes can be
differentiated only by mass, charge, and angular momentum.
b. they always occur at the end of a
starŐs life when more than ~1.2 solar masses remain in the core.
c. there will
be very strong tidal forces as one approaches the event horizon, at least for
stellar sized black holes.
d. they are
typically identified by studying the emissions from the matter being accreted
in disks close to the event horizon.
e. would look
like a giant whirlpool funnel in space.
9. Concerning
the Space Time Diagram:
a. you can
always choose to stay at here-now without moving since that
clearly is slower than the speed of light.
b. at here-now
you can only affect events that will occur in your future.
c. elsewhere
is not in our universe.
d. as you move
into your future some of what was in elsewhere can become part of your past at
your new here-now, but parts of elsewhere can never become part
of your future.
e. the future
and past are indistinguishable.
10. General
Relativity:
a. is
EinsteinŐs theory that gravity is due to the effect that the local energy
density has on the geometry of space-time.
b. still
assumes that light moves in ŇstraightÓ lines, but predicts that the straight
lines are bent.
c. predicted
neutron stars long before there was any evidence that they actually existed.
d. Has been
used to show how all of the laws of physics can be interpreted as simple
geometric effects.
e. allows the
other forces to remain, but treats gravity as not being a force.
11. The
sunspot cycle:
a. is a result
of the Sun's periodic magnetic field reversals and the winding up of the
magnetic field due to the SunŐs differential rotation.
b. has been
observed closely for only the last 100 years.
c. can vary
considerably in the total number of spots from one cycle to the next.
d. actually
requires about 22 years for the total true cycle period.
e. is
basically confined entirely to the SunŐs photosphere.
12. The
giant branch on an HR diagram:
a. is located
strictly above and to the right of the main sequence for both Population I and
II stars.
b. contains
stars whose surface temperatures are all higher than the sun's.
c. contains
all of the red stars on the HR diagram.
d. has stars
that are all burning helium somewhere inside.
e. may also
contain many very bright blue stars.
13. Pre-T-Tauri
stars:
a. appear
first in the UV wavelengths at the extreme lower right hand edge of the HR
diagram.
b. have not
yet reached the main sequence.
c. also
proceed through the RR-Lyrae variable stage prior to reaching the main
sequence.
d. all known
present examples in the Milky Way are Population I (high heavy element
abundance) type stars.
e. generally
slow their rate of contraction because of radiation flow outward from heating
due to their gravitational contraction.
14. Brown
Dwarfs:
a. are plotted
at the extreme lower left-hand corner of an HR diagram.
b. are all
main sequence stars.
c. are
actually Ňfailed stars.Ó
d. include
Jupiter.
e. are all
thought to be the final evolutionary state of the lowest mass Main Sequence
stars.
15. Population
II stars in our galaxy:
a. generally
are all very young.
b. have
roughly the same age distribution as Population I stars.
c. contain a
slightly larger fraction of their total mass as Hydrogen than do Population I
stars.
d. cannot
participate readily in the C-N-O process even when they have sufficient mass.
e. have HR
diagrams that are generally identical to those of Population I stars.
16. With
regard to the Sun's atmospheric layers:
a. the
chromosphere lies directly above the photosphere.
b. the upper
boundary of the photoshpere is cooler than its lower boundary.
c. they each
have compositions that are similar to the air in this room.
d. the
photosphere is the region where 99% of the total light we see is emitted.
e. the maximum
temperature that occurs in each successive layer increases as one moves outward
from the surface of the Sun.
17. Fermions:
a. Obey the
Exclusion Principle.
b. are never
conserved by type.
c. are the
fundamental Ňbuilding blocksÓ of our universe.
d. are all
electrically charged.
e. Obey the
Uncertainty Principle.
18. Concerning
the Solar Neutrino Experiment that was done in the South Dakota mine, which of the
following are true:
a. the
detector contained common soap-like laundry detergent as a source of neutrinos.
b. it required
a deep mine so that it is very dark and no sunlight can get in.
c. it found
too few neutrinos when compared with theoretical predictions.
d. detected
neutrinos by looking for 37Ar
produced as a result of neutrino interactions.
e. it
attempted to "detect" neutrinos coming directly from the surface of
the Sun.
19. Cepheid
variable stars:
a. are
variable stars with an average luminosity about the same as the SunŐs.
b. have a
rapidly varying energy source in their cores which cause the variation in the
luminosity.
c. reach the
most dim point in their light curve when their atmospheres are the most
contracted.
d. are all
main sequence stars.
e. tend to
have period-luminosity relationships that make them very useful as distance
indicators.
20. During
post main sequence evolution:
a. elements
heavier than helium can be produced.
b. the
remaining lifetime is much shorter than the same star's main sequence lifetime
had been.
c. all stars
will become extreme Population I stars in their surface spectrum.
d. some stars
continue to burn hydrogen in their innermost cores.
e. all stars
tend to increase their masses slightly.
21. Fusion:
a. when it
results in the binding of previously unbound objects it must always be
accompanied by a release of energy.
b. refers to
either the putting together of small objects or the breaking apart of big ones.
c. results in
a net decrease in the total mass if the resulting object is more tightly bound
than the prior objects might have been.
d. has never
occurred on or near the earth, but only in the sun's core.
e. increases
the net amount of energy in the universe.
22. Nucleosynthesis
(fusion of smaller nuclei into larger ones) in stars:
a. Tends to
result in the production of the Uranium nuclei on the periodic table over Lead
nuclei.
b. Releases
most of the energy in the form of neutrinos during the synthesis of the smaller
nuclei.
c. can release
net energy all the way up to Uranium (U, Atomic Number = 92) nuclei.
d. is occuring
in the core of an isolated white dwarf.
e. Produced
all of the elements in your body heavier than hydrogenÉ
23. Concerning
the SunŐs interior
a. Energy is
transported principally via radiation in the region just below the visible
surface.
b. Energy is
transported via radiation in the Convective Zone.
c. The
Radiative Zone is hotter and denser than the Convective Zone.
d. The net
luminosity of the core is essentially the same as that at the SunŐs surface.
e. We cannot
see any light coming directly from the interior, (by definition).