Download Astronomy 3020: Cosmology Samples for Exam 3

Astronomy 3020: Cosmology
Samples for Exam 3
Chapter 4
1.
Which of the following statements is false?
a) Refraction is the bending of light when it passes from one medium to another.
b) The product of the wavelength of a wave times its frequency is equal to the
waves’ speed of propagation.
c) Reflection is the “bouncing” of light off a surface.
d) Interference between two waves only occurs if the waves have the same
frequency.
2.
The Doppler Effect is
a) the change in observed wavelength of a wave when the source is moving with
respect to the observer.
b) the change in the observed intensity of a wave when the source is moving
with respect to the observer.
c) the change in the observed speed of light when the source is moving with
respect to the observer.
d) the change in the observed position of a star due to the relative motion of the
earth around the sun.
3.
Blackbody radiation is
a) the individual wavelengths of light emitted from black holes.
b) the individual wavelengths of light that are absorbed by objects that are
painted black.
c) the continuous spectrum of light that is emitted from objects due to their
temperature.
d) the individual wavelengths of light that are emitted from objects due to their
mass.
4.
The electromagnetic spectrum is
a) part of a large electromagnet.
b) the entire range of “light” from gamma rays to very long radio waves.
c) visible light.
d) “light” that is not visible to the human eye.
5.
Atoms emit light when
a) an electron spontaneously falls from a high to a low energy state.
b) an electron spontaneously jumps from a low to a high energy state.
c) an electron completes one orbit around the nucleus.
d) an electron is thrown out of the nucleus.
7.
The brightness of a celestial object depends
a) only on the distance to the object.
b) only on the absolute luminosity of the object.
c) both the distance and absolute luminosity of the object.
d) neither the distance nor the absolute luminosity of the object.
Essay Questions
1. Describe the process of reflection, refraction, interference and diffraction. How
does each process work and what is the fundamental cause?
2. Describe a blackbody spectrum. What kinds of objects produce blackbody
spectra? What factors affect the shape of a blackbody spectrum and how do they
affect it?
Chapter 5
1.
Stars are formed in
a) deep space that is free of all dust and gas.
b) cold dark clouds of gas and dust.
c) deep space that contains hot ionized gas.
d) in the cores of red supergiants.
2.
Which of the following statements is false?
a) As the solar nebula began to collapse under its own gravity it began to spinup due to the conservation of angular momentum.
b) As the solar nebula began to collapse under its own gravity it began to flatten
out into a disk shape with a central bulge.
c) Protoplanetary disks are infant solar systems in the process of forming.
d) Newly forming solar systems have never been observed anywhere in the
universe.
3.
A brown dwarf star is
a) a star-like object that has not yet begun to fuse hydrogen but is still collapsing
and will eventually fuse hydrogen.
b) a star-like object that does not have sufficient mass to ever reach a core
temperature high enough to fuse hydrogen.
c) a star-like object that has fused all the hydrogen in its core and has begun to
shrink and cool off.
d) a star-like object that is fusing hydrogen into helium in its core.
4.
The primary energy source in the sun is
a) the fusion of hydrogen into helium in the core.
b) the burning of carbon (as coal) in the core.
c) the residual energy left over from gravitational collapse.
d) the fission of uranium into two smaller atoms in the core.
5.
Hydrostatic equilibrium occurs in stars because
a) the rate of energy production in the core is balanced by the inward pressure
due to gravity.
b) the outward pressure of neutrinos produced in the core balances the inward
pressure of gravity.
c) the rate of energy production in the core is insufficient to balance the inward
pressure of gravity.
d) the force of gravity causes the core of a star to shrink and heat up.
6.
Stars consist of
a) a mixture of all the elements in equal portions.
b) mostly helium (74%) and carbon (25%) with traces of all other elements.
c) mostly hydrogen ( 74%) and helium (25%) with traces of all other elements.
d) a degenerate neutron gas.
7.
The proton-proton cycle is
a) the fusion of four hydrogen into a single helium plus two positrons and energy
through several steps.
b) the fusion of three helium into a single carbon through several steps.
c) the fusion of two protons into a helium.
d) the emission of electromagnetic radiation due to a transition from one energy
level to another by a pair of protons.
8.
In general, the more massive the star
a) the smaller it will be.
b) the cooler it will burn.
c) the more luminous it will be.
d) the farther away it is.
9.
Main sequence stars are
a) stars whose mass is less than 5 solar masses.
b) stars of all masses which are burning hydrogen in their core.
c) stars whose mass is greater than 5 solar masses.
d) stars which are more luminous than the sun.
e) stars which are less luminous than the sun.
10.
The Hertzsprung-Russell diagram is
a) a plot of mass versus luminosity of stars.
b) a plot of luminosity versus temperature of stars.
c) a plot of luminosity versus distance of stars.
d) a plot of mass versus temperature of stars.
11.
Population II stars are
a) young stars that are “metal” rich.
b) old stars that are “metal” poor.
c) young stars that are “metal” poor.
d) old stars that are “metal” rich.
12.
The H-R diagram of a very old globular cluster will have
a) only low mass main sequence stars, a few red giants and lots of white dwarf
stars.
b) stars scattered all over the graph with a large number of supergiants and
white dwarfs as well as main sequence stars of all mass.
c) main sequence stars up to 4 or 5 solar masses along with red giants and
white dwarfs.
d) main sequence stars of all masses and very few of any other types.
13.
A white dwarf star is composed of
a) pure neutrons.
b) elements heavier than iron.
c) a degenerate electron gas of mostly carbon and oxygen.
d) a degenerate electron gas of hydrogen.
14.
The Chandrasekhar limit is
a) the maximum mass of a white dwarf star.
b) the minimum mass of a white dwarf star.
c) the maximum mass of a neutron star.
d) the maximum mass of a black hole.
15.
A Type Ia supernova occurs for
a) a black hole.
b) a low mass red dwarf.
c) a star on the main sequence.
d) a white dwarf in a binary system.
16.
A Type II supernova occurs for
a) a lone white dwarf.
b) a black hole.
c) a low mass red dwarf.
d) a massive red or blue supergiant.
17.
A neutron star is composed of
a) a degenerate electron gas of carbon.
b) a degenerate electron gas of helium.
c) a degenerate neutron gas.
d) a degenerate proton gas.
18.
A pulsar is a
a) slowly rotating black hole.
b) rapidly rotating neutron star.
c) a dying white dwarf.
d) a new born star (a ZAMS).
19.
A pulsar “pulses” because
a) the star is undergoing rapid increases and decreases in its surface
temperature and diameter.
b) the fusion process at the surface of the star is turning on and off at a rapid
rate.
c) the “light” from the star is being emitted from the magnetic poles of the star
that are rotating around at a rapid rate.
d) the “light” from the star is turning on and off at a rapid rate for some unknown
reason.
20.
A millisecond pulsar is one that
a) has spun down to a period of millions of seconds.
b) has spun up to a period of thousandths of a second by accreting mass from a
companion star.
c) has maintained its period exactly for millions of years.
d) has spun up to a period of days by radiating energy out along the poles of its
magnetic field.
Essay Questions
1. Sketch an H-R diagram. Assume you are plotting a sample of 100 stars that are
a good representation of all stars. Label the areas of the different luminosity
classes on your diagram.
2. Describe the formation of a star from a clump of gas and dust in a GMC through
the protostar stage and finally to a full-fledged star.
3. Describe the lifecycle of a one solar mass star from a zero age main sequence
star to the end of helium burning.
4. Describe some of the difference between regular matter and degenerate matter.
5. Describe a white dwarf star. What is it composed of? How big is it? How does its
size depend on its mass? How does it evolve?
6. Describe a Type Ia supernova. What kind of star does it occur for, what is the
difference between it and an ordinary nova, what is left behind after the
supernova?
7. Describe the lighthouse model of a pulsar. Why does it pulse, what causes it to
radiate, what are the typical periods of the pulses and how long do the pulses
last?
8. Explain the Black Widow pulsar. How fast does it spin, how is its spin rate
changing and why is the rate changing? Why is “Black Widow” an appropriate
name for it?
Chapter 6
1.
The Copernican Principle is
a) There is nothing special or unique about Earth.
b) Earth is at the center of the universe.
c) The Sun is at the center of the universe.
d) The universe is infinite and has no center.
2.
The weak anthropic principle states
a) The conditions in the universe exists because we are here.
b) The conditions in the universe are compatible with our existence.
c) The conditions in the universe are incompatible with our existence.
3.
The strong anthropic principle states
a) The conditions in the universe exists because we are here.
b) The conditions in the universe are compatible with our existence.
c) The conditions in the universe are incompatible with our existence.
4.
Something is isotropic if it is
a) the same everywhere.
b) not the same everywhere.
c) the same in all directions.
d) not the same in all directions.
5.
Something is homogeneous if it is
a) the same everywhere.
b) not the same everywhere.
c) the same in all directions.
d) not the same in all directions.
6.
If you could be instantaneously transported 13 billion lightyears away from Earth,
you would see
a) the same kinds of stars and galaxies you see here, just different patterns.
b) the region around you filled with glowing hot gas from the Big Bang.
c) nothing if you looked in the direction opposite the Earth since you would be at
the edge of the universe.
d) stars and galaxies unlike any we see around Earth.
7.
The cosmological principle states that the universe
a) is isotropic and homogeneous and the laws of physics are the same
everywhere.
b) Is isotropic but not homogeneous because the laws of physics are not the
same everywhere.
c) is homogeneous but not isotropic because the plane of the Milky Way defines
a preferred direction.
d) is isotropic and homogeneous in space but not in time since the laws of
physics have evolved in time.
8.
An inertial frame of reference is one in which a particle will undergo
a) straight line uniform motion when a net force is applied to it.
b) straight line accelerated motion when no force is applied to it.
c) straight line uniform motion when there is no net force acting on it.
d) curved motion when a net force acts on it.
9.
Which of the following is a manifestation of the surface of the Earth being a noninertial reference frame?
a) The Coriolis Effect
b) The Doppler Effect
c) The Butterfly Effect
d) The Crystal Effect.
10.
Which of the following is not an inertial reference frame?
a) A spacecraft moving at constant speed in deep space.
b) A rock undergoing freefall near the surface of a non-rotating planet.
c) A person standing still on the surface of the Earth.
11.
Which of the following quantities requires a Galilean transformation from one
inertial reference frame to another?
a) The velocity of an object
b) The mass of an object
c) The acceleration of an object
d) The force acting on an object
12.
The Michelson-Morley experiment
a) proved that the luminiferous ether exists.
b) proved that the speed of light was the same in all directions.
c) proved that light behaved differently than mechanical objects.
d) proved that the Earth was a preferred reference frame.
13.
Which of the following papers was not published by Albert Einstein in 1905?
a) A paper on Brownian motion
b) A paper on the photoelectric effect
c) A paper on the electrodynamics of moving bodies
d) The General Theory of Relativity.
Essay Questions
1. Describe the anthropic principle. What is the difference between the weak
anthropic principal and the strong anthropic principal?
2. Describe the Cosmological Principle. Include a description of “homogeneous”
and give examples of homogeneous systems that are and are not isotropic. Why
is it important to have a cosmological principle?
3. What is meant by an “inertial reference frame”? On what size scale is our
reference frame inertial and on what size is it not? What are some of the
consequences of being in a non-inertial reference frame?
4. Describe the Michelson-Morley experiment. What did they attempt to measure
and how did they measure it? What were their results? What was the significance
of their results?
Chapter 7
1.
One of the basic principles of Einstein’s Special Relativity is
a) The speed of light depends on the relative speed between the source and the
observer.
b) It is always possible determine who is moving and who is stationary.
c) The observed laws of physics are the same regardless of any constant
velocity at which you move.
d) It is possible to move at speeds greater than the speed of light.
e) All of the above.
2.
If an observer is stationary on the surface of the Earth and watches a spacecraft
moving past at 9/10 the speed of light he sees
a) the stationary observer sees the moving clock as running fast.
b) the stationary observer sees the moving clock as running the same speed as
his clock.
c) the stationary observer sees the moving clock as running slow.
3.
Others had proposed a Lorentz transformation to solve the problem of the speed
of light before Einstein. Most scientists were reluctant to accept this because it
a) seemed too arbitrary and there was no physical explanation for it.
b) violated Newtonian absolute space and time.
c) only applied to electromagnetic systems and not mechanical systems.
d) did not give the same answer as ordinary Galilean transformations when the
relative speed was small as compared to the speed of light.
e) None of the above, the Lorentz transformation was widely accepted even
before Einstein published his special theory of relativity.
4.
An observer on a moving train sees two flashes of lightning strike the front and
rear of his train car simultaneously. An observer on a platform watching the train move
past sees
a) the two flashes of lightning strike the ends of the train simultaneously.
b) one flash striking the rear of the train first then a second flash strike the front
of the train later.
c) one flash strike the front of the train first and then a second flash strike the
rear of the train later.
5.
In Special Relativity, if I see your clock as running slow, you will see
a) your clock as running slower than my clock.
b) my clock as running slower than your clock.
c) your clock as running faster than my clock.
d) both our clock as running at the same speed.
6.
Proper time is the time
a) measured by a clock that is stationary with respect to inertial observer.
b) that is measured by a clock that is stationary with respect to the luminiferous
ether.
c) measured by a clock that is moving at the speed of light with respect to the
observer.
d) that is measured by any clock that is moving are an arbitrary speed with
respect to the observer.
7.
If the space-time interval between two events in space-time is an imaginary
number, they are said to have a
a) a time-like separation.
b) imaginary separation.
c) space-like separation.
d) no separation.
8.
In the twin paradox where one twin takes a voyage to Alpha Centauri at close to
the speed of light while the other stays at home, the twin that takes the voyage is the
younger at the end because
a) She observed her stay-at-home brother’s clock to be running fast during the
entire time of her trip
b) He observed his travelling sister’s clock to be running very slow as she was
acceleration away from Earth, turning around at Alpha Centauri and slowing
down as she approached Earth but running slightly fast for the rest of her trip.
c) She observed her stay-at-home brother’s clock to be running fast as she
accelerated away from Earth, slowing down approaching Alpha Centauri,
accelerated away from Alpha Centauri and slowing down approaching Earth
but running slow for the rest of her trip.
d) None of the above, they are both younger and that is the paradox.
9. An observer on the Earth sees a spaceship moving east at 0.8c and another moving
west at 0.9c. If a passenger on the spaceship moving west shines a laser at the
spaceship moving east, which of the following is not possible?
a) A passenger on the spaceship moving east measures the speed of the laser
to be exactly 2.998x108 m/s.
b) The observer on the Earth measures the speed of the laser to be exactly
2.998x108 m/s.
c) A passenger on the spaceship moving west observes clocks aboard the
spaceship moving east to be running fast.
d) The observer on the Earth observes clocks on both spaceships to be running
slow but at different rates.
Essay Questions
1. Briefly discuss Einstein’s Special Theory of Relativity. What are the basic
assumptions of the theory? What are some of the consequences of the theory on
objects that are moving at speeds close to the speed of light?
2. Describe the Lorentz transformations and how they are applied to time dilation,
length contraction and velocity addition. Discuss the meaning of these
transformations. Use the example of Isaac, who is stationary on the surface of
the Earth, observing Albert on a rocket speeding past the Earth at 0.99c to
describe what each one sees.
3. Describe the relativistic Doppler Effect. What is the difference between the
classical Doppler Effect and the relativistic Doppler Effect?
4. Describe a Minkowski diagram. Draw a simple 1-D Minkowski diagram and label
“past” and “future”, time-like and space-like separations and the light cone.
5. Describe the twin paradox. Why is the paradox not really a paradox? Use a
Minkowski diagram for the stay-at-home twin to illustrate the twin paradox.
Chapter 8
Essay Questions
1. Describe the anomalous precession of the perihelion of Mercury. How was the
anomalous precession explained (or attempted to be explained) using Newtonian
gravity and mechanics.
2. Briefly discuss Einstein’s General Theory of Relativity. What is the difference
between General Relativity and Special Relativity? What is the basic principle of
General Relativity? What are some of the consequences of General Relativity?
3. Describe the equivalence principle. What is the difference between the weak
equivalence principle and the strong equivalence principle? Describe how the
equivalence principle can lead to gravitational redshift and gravitational length
contraction.
4. Discuss why it is necessary to use geometry to describe general relativity. What
is meant by the “metric” and what is the general metric for space-time? What is a
geodesic and why is it important? What types of geometries are important for
general relativity and what property do they have in common?
5. Write out the simplified form of the equation of general relativity. Explain what
each of the terms is and how it is written out in the full form.
6. Describe in some detail at least two of the experimental tests of the theory of
General Relativity.