+16 Physics 112
+16 Practice Final Exam
+16 Spring 2004

1. What are the characteristic features on the visible surface of Jupiter?
A.Light and dark bands of clouds parallel to the equator.
B.Large volcanoes and a long, deep rift valley.
C.A Bluish-green, almost featureless, cloud layer.
D.A bluish tint with high, white clouds and dark storms.

2. The interesting feature of Jupiter's rotation is the fact that
A.its rotation rate has slowed down significantly since it was first observed through telescopes in the 1600s.
B.it rotates in a direction opposite to that of most of the planets and opposite to its direction of revolution around the Sun.
C.its axis of rotation lies almost in the plane of its orbit.
D.regions at different latitudes appear to rotate at different rates.

3. Jupiter has a magnetic field that is
A.almost nonexistent.
B.much more powerful than that of Earth.
C.about the same strength and extent as that of Earth.
D.weak and variable, sometimes existing only at the Great Red Spot.

4. Why would you expect to see no craters, such as those on the Moon or Mars, on Io, the innermost Galilean moon of Jupiter?
A.Because volcanoes are continuously depositing new material onto the surface.
B.Because the surface is always re-entering the planet's interior by subduction in rapid plate tectonic motion, similar to but faster than that upon Earth.
C.Because the continuous H2O rainfall will quickly erode and wash away all trace of craters.
D.Because the liquid surface cannot maintain a crater, just as the Earth's oceans cannot do so.

5. The rings of Saturn are seen by
A.fluorescence, a glow produced by photochemistry when material is irradiated by solar UV light and/or high-speed cosmic particles.
B.emitted light from the molecules of the material of the rings, such as methane, ammonia etc..
C.reflected and scattered sunlight.
D.reflected light from Saturn, since we can see them at night.

6. The asteroid belt is believed by most astronomers to be composed of
A.the remnants of a gaseous planet, disrupted by a massive impact.
B.genuine leather.
C.rather dirty ice-balls similar to the nuclei of comets.
D.rocky debris left over from the formation of the solar system.

7. In a single photograph of a comet and its tail, the only direction that one can determine with certainty is
A.the direction away from the Sun, since the tail is pushed in this direction by the solar wind.
B.the direction towards the Sun indicated by the tail direction, since gas and dust in the tail is attracted towards the Sun by its gravity.
C.the direction towards Jupiter, since the gravity of this giant planet pulls the tail material towards it.
D.the direction in which the comet is moving, from the trailing tail.

8. What name is given to the visible "surface" of the Sun?

9. The visible corona of the Sun is most effectively photographed
A.in spring and fall seasons, because of the tilt of the spin axis of the Sun.
B.during lunar eclipses, when the sky is darker.
C.during solar eclipses.
D.at solar maximum periods, over a period of a few years.

10. Galileo observed the phenomenon of solar rotation in the early 1600s by
A.measuring the Doppler shift of hydrogen spectral lines from the E and W limbs of the Sun.
B.watching bright regions of hydrogen gas drift across the Sun.
C.noting the periodic (monthly) variation of auroral disturbances or northern lights.
D.measuring the motion of sunspots across the solar surface.

11. The Zeeman effect describes the shift in wavelength of light caused by
A.relative motion of the source and observer.
B.magnetic fields acting on the radiating atoms.
C.the extreme mass and gravitational field of the source.
D.the light passing through a transparent medium.

12. What is the source of the x-ray emitted by the solar corona?
A.High-energy charged particles spiraling along the coronal magnetic fields.
B.Radioactivity in the coronal gases.
C.X-ray from the solar photosphere scattered from ions in the corona.
D.The high temperature gas of the corona.

13. The solar wind is ionized gas flowing outward
A.only from solar flares.
B.from sunspots.
C.primarily through coronal holes.
D.more or less uniformly from the entire solar surface.

14. What process provides the power for the Sun?
A.The fission of uranium to form lead.
B.The fusion of helium into carbon.
C.The fusion of hydrogen into helium.
D.The emission of neutrinos.

15. In the thermonuclear process that is thought to heat the Sun, the nuclei of which chemical elements are converted to other nuclei to produce the requisite energy?
A.Hydrogen converted to helium.
B.Iron, in a chain reaction, leading eventually to hydrogen.
C.Helium converted to hydrogen.
D.Uranium converted to lead.

16. Which of the following physical products are not produced by the Sun during the thermonuclear processes in which hydrogen nuclei are combined together in its core?
B.Positive electrons, or positrons.
C.Helium nuclei.
D.Heavy nuclei such as uranium.

17. Approximately where is the Sun in terms of its total lifetime?
A.It is about 1/4 of the way through its life.
B.It is about 1/10 of the way through its life.
C.It is about 3/4 of the way through its life.
D.It is about half way through its life.

18. As you drive along a road, trees in the middle distance seem to shift in position relative to far-away hills. What name is given to this phenomenon?
A.The inverse-square law.
B.The Doppler effect.

19. How far away is the nearest star beyond the Sun?
A.Between 1 and 2 light years away.
B.About 4 light years away.
C.About 1/4 light year away
D.About 1/10 light year away.

20. To match the light intensity from a first-magnitude star would require the equivalent light from how many second-magnitude stars?
A.About 10
B.About 0.4, or 1/2.5
D.About 2.5

21. In order for absorption lines in the Paschen series of hydrogen to be seen in the IR spectrum of a star (see Sec. 4-6 of Kaufmann & Comins, Discovering the Universe, 5th Ed.), the temperature of its surface must be high enough to excite electrons by collision to the
A.n = 3 energy level.
B.n = 2 energy level.
C.n = 4 energy level.
D.ionization level.

22. The spectrum of a very distant star shows spectral absorption lines of ionized helium, He II, AND molecular absorption bands from titanium oxide, TiO. What would be your conclusion about this star?
A.There must be cool, interstellar gas containing TiO between the star and Earth.
B.It is obviously the spectrum of a binary system, two stars close together, a hot star and a cooler companion, unresolved as separate stars from our distance but contributing separate spectra.
C.There must be a very hot atmosphere containing helium gas, overlying a much cooler stellar surface.
D.The star must have a thick, cool atmosphere overlying a hot stellar atmosphere.

23. Compared to a star in the middle of the Hertzsprung-Russell diagram, a star in the upper right part of the diagram is
D.non-existent, since there are no stars which appear in the upper right part of the diagram.

24. Where are the most massive stars to be found in the main sequence of a Hertzsprung-Russell diagram?
A.Main sequence stars all have approximately the same mass, by definition.
B.The lower, right end.
C.In the center section near to the Sun's position, with lower mass stars on either side.
D.The upper, left end.

25. The radial-velocity curve of a star in a binary star system is a plot against time of
A.the variation of Doppler shift of its spectral lines, and hence of its speed towards or away from us.
B.the speed of the star in a direction perpendicular to the line of sight to the star.
C.the position of the star in celestial coordinates.
D.the temperature of the star as determined from the movement of the peak wavelength of its spectrum.

26. What particular and very important phenomenon frequently occurs in binary star systems where the stars are very close together?
A.The less massive star spirals slowly into its more massive companion because of tidal interactions.
B.The radiation from the hotter star will slowly heat and evaporate away the cooler star.
C.The less massive star, in its elliptical orbit, will repeatedly pass through the thin, extended atmosphere of the second star, producing periodic rises and falls in light output from the star system.
D.Mass lost from one star is deposited upon its companion.

27. The space between stars is known to contain
A.variable amounts of gas but no dust, which only forms in planetary systems near stars.
B.dust and gas, both atomic and molecular.
C.a perfect vacuum.
D.large quantities of dust that absorb light, but no gas, either atomic or molecular.

28. What determines whether a particular region of an interstellar cloud can collapse and form a star?
A.The amount of gravity pulling inwards compared to gas pressure pushing outwards.
B.Only the temperature, since higher temperatures act to prevent collapse.
C.Only the amount of mass in the cloud, since this determines the strength of gravity.
D.How the mass of the cloud compares to its diameter, since this determines how gravity compares to the distance needed to collapse.

29. Protostars are
A.slowly contracting and heating up.
B.slowly contracting and cooling.
C.slowly heating up and expanding.
D.slowly expanding at the surface while the core contracts.

30. What is the lowest mass that an object can have and still be a star?
A.0.02 solar masses.
B.0.80 solar masses.
C.0.002 solar masses (twice Jupiter's mass).
D.0.08 solar masses.

31. In the Hertzsprung-Russell diagram, how does the position of a typical star change while it is at the main sequence phase of its evolution?
A.A star's position on the main sequence is determined only by its mass and not its age, and so, stars do not move along the main sequence during evolution.
B.Massive stars (4 solar masses) move toward the upper left as their luminosity increases, while lower-mass stars move toward the lower right as their temperature decreases.
C.Stars move from upper right to lower left while they are on the main sequence.
D.Stars move from upper left to lower right while they are on the main sequence.

32. In terms of the mass and lifetime of a star, which of the following statements is true?
A.The more massive the star, the faster it will evolve through its life.
B.The mass of a star has no bearing on the length of a star's life or the speed of its evolution.
C.Stars of about one solar mass have the shortest lives; less massive stars evolve slowly and live a longer time, while more massive stars have long lives because of the large amount of fuel which they contain.
D.The less massive the star, the shorter its life, because it has less hydrogen "fuel" to burn.

33. In terms of nuclear reactions, what is the next stage of a star's life after the end of hydrogen burning in the core?
A.Hydrogen burning in a thin shell around the core.
B.Helium burning in the core.
C.Carbon burning.
D.Death (it becomes either a supernova or a white dwarf).

34. The Pauli exclusion principle
A.limits the number of atoms which can become ionized in a star.
B.prevents two stars of the same spectral class from occupying the same binary star system.
C.prevents high-mass stars from forming in low-mass interstellar clouds.
D.sets a limit to the crowding together of electrons into any given small volume of space.

35. What is the "safety valve" which operates in normal (nondegenerate) stars?
A.If the stellar gas is suddenly heated, it will expand and cool.
B.If the pressure gets too high, electrons will combine with protons to relieve the pressure.
C.If thermonuclear reactions proceed too quickly, the star will run out of fuel before anything drastic happens.
D.If the star gets too big, it will collapse into a black hole.

36. The helium flash results from the
A.high temperature in the helium core of a blue (spectral class O or B) supergiant star.
B.electron degeneracy or quantum crowding in the core of a low-mass red giant star.
C.sudden onset of nuclear reactions at the end of the protostar.
D.sudden release of energy in strong magnetic fields near a sunspot.

37. The time taken for neutrinos generated in the thermonuclear reactions at the center of the Sun to escape from its surface is
A.about 1 million years.
B.about 1 year.
C.instantaneous, since they travel faster than the speed of light.
D.a few seconds.

38. What would you expect to find in the population of stars in a globular cluster?
A.Many red giants, white dwarfs and dim red stars, but no dust and gas.
B.Stars along the entire main sequence from bright blue to dim red, with no bright red giant stars but significant amounts of dust and gas.
C.Mainly white dwarf stars and the planetary nebular stages of dying stars, but no faint red stars, red giants or bright blue stars.
D.Mostly blue giants and supergiants, with a few red giant stars, white dwarfs, and dim red stars.

39. What scientific method is used to observe the pulsation in size of a Cepheid variable star?
A.The observed perturbations in the orbits of planets around these stars.
B.This behavior has only been predicted theoretically, and has never been detected.
C.Doppler shift of absorption lines in its spectrum.
D.The observed increase and decrease in the size of the star's image.

40. Which factor, more than any other, modifies the evolutionary tracks of stars in binary combinations compared to their single star counterparts?
A.Tidal distortion of the shapes of the stars.
B.Reduction of the quantum mechanical limitation on continued shrinking of one star by the gravitational field of the second star.
C.Mass exchange between the stars.
D.Radiation from one star heating the surface of the second star.

41. What are the main by-products of helium nuclear "burning" in red giant stars?
A.Hydrogen nuclei, by nuclear fission.
B.Energy, from the complete transformation of the mass of helium to energy.
C.Carbon and oxygen nuclei.
D.Iron nuclei.

42. The energy generation process inside a white dwarf star is
A.non-existent; a white dwarf star is simply cooling by radiating its original heat.
B.the combining of protons and electrons to form neutrons within its core.
C.hydrogen fusion.
D.the helium flash; very efficient and rapid helium fusion.

43. One peculiar feature of the evolution of a white dwarf star of a particular mass is that
A.its size or radius remains constant as it cools and dies.
B.it shrinks as it cools, eventually to become a cold black hole in space.
C.it heats up as it shrinks because of the release of gravitational energy, ending up as a very hot but very small star.
D.its size or radius slowly increases as it cools, until it ends up as a red giant star.

44. A sequence of thermonuclear "burning" and fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon, oxygen, etc. into heavier nuclei AND also generate excess energy, up to a limit beyond which no further energy-producing reactions can occur. The element that is produced when this limit is reached is

45. After the material in the core of a massive star has been converted to iron by thermonuclear reactions, further energy can be released to heat the core ONLY by
A.nuclear fission or splitting of nuclei.
B.gravitational contraction.
C.thermonuclear fusion of iron into heavier elements.
D.the absorption of neutrinos.

46. Can a white dwarf explode?
A.Yes, but only if another star collides with it; and stars are so far apart in space that this is unlikely to have ever happened in our galaxy.
B.Yes, but only if it is in a binary star system.
C.No; white dwarfs are held up by electron degeneracy pressure, and this configuration is stable against collapse or explosion.
D.Yes, but only if nuclear reactions in the white dwarf core reach the stage of silicon burning, producing iron.

47. A pulsar is
A.an accretion disk around a black hole, emitting light as matter is accumulated onto the disk.
B.an very precise interstellar beacon manufactured by little green humanoid life forms.
C.a type of variable star, pulsating rapidly in size and brightness.
D.a rapidly spinning neutron star.

48. The diameter of a typical neutron star of 1 solar mass is predicted to be approximately
A.that of an average city, a few km.
B.1 km.
C.that of Earth, 12,800 km.
D.that of the Sun.

49. The escape velocity of matter from near the center of a black hole whose mass is 3 solar masses is
A.quite small.
B.about half the speed of light.
C.much greater than the speed of light.
D.always exactly equal to the speed of light.

50. Suppose you were far from a planet that had a very strong gravitational field, and you were looking at a source of hydrogen (H-alpha) light on the surface of the planet. When you observe an H-alpha light source in your own spaceship, the wavelength is 656.3 nm. What wavelength do you see when you look at the light source on the planet?
A.Longer than 656.3 nm.
B.Shorter than 656.3 nm.
C.Infinite wavelength, since the source is in a gravitational field.
D.656.3 nm, the same as from your light source.

51. Where would you look for a supermassive black hole?
A.At the center of a supernova remnant.
B.Orbiting a normal star in our galaxy.
C.In the center of a galaxy.
D.At the center of the universe.

52. What separates a black hole from the rest of the universe?
A.Its crystalline crust.
B.The surface of the ergosphere.
C.The event horizon.
D.The singularity.

53. Which one of the following statements about the evaporation of black holes is correct?
A.The rate at which a black hole evaporates is lower for a higher-mass black hole.
B.The rate at which a black hole evaporates is higher for a higher-mass black hole.
C.Black holes do not evaporate.
D.The rate at which a black hole evaporates is independent of the mass of the black hole.

54. The intrinsic brightness (represented by luminosity) of a Cepheid variable star compared to that of the Sun is
A.significantly less.
B.several thousand times larger.
C.about the same.
D.about 10 times larger.

55. Galaxies throughout the Universe appear to be distributed
A.mostly in a single spherical shell surrounding a void in space, presumed to have been caused by a vast
B.uniformly throughout space.
C.in groups and surfaces surrounding vast voids, much like the surfaces of giant bubbles.
D.around a single point in space, the presumed location of the original Big Bang, which created the Universe.

56. Radio waves of 21-cm wavelength originate from which component of the interstellar medium?
A.Cool, carbon monoxide, CO.
B.Cold, molecular hydrogen, H2.
C.Hot, ionized atomic hydrogen.
D.Cool, neutral atomic hydrogen.

57. The Sun's position in the galaxy is
A.we cannot tell where we are located because our view is too severely restricted by interstellar dust.
B.in the disk of the Galaxy, inside a spiral arm or segment of a spiral arm.
C.in the disk of the Galaxy, between and well away any spiral arm.
D.in the spherical halo, somewhat above and outside of the spiral arms.

58. Much of the mass of our Galaxy appears to be in the form of "dark" matter of unknown composition. At present, this matter can be only detected because
A.its gravitational pull affects orbital motions in the Galaxy.
B.it blocks out the light from distant stars in the plane of our Galaxy.
C.it bends light from distant quasars.
D.it emits synchrotron radiation at radio wavelengths.

59. Which two quantities are shown to be related to one another in Hubble's Law?
A.Distance and brightness.
B.Distance and recession velocity.
C.Brightness and recession velocity.
D.Brightness and the width of the 21-cm radio emission line of hydrogen.

60. "Standard candles," which are important for finding distances to remote galaxies, are
A.stars and other objects of known intrinsic brightness.
B.standard laboratory light sources with which the brightness of a galaxy can be compared.
C.heat sources used for calibrating infra-red observations of galaxies.
D.standard bars of known length with which the size of a galaxy can be measured.

61. What appears to be the central energy-generating system or "engine" that is producing prodigious amounts of energy in the centers of galaxies, active galaxies and quasars?
A.A supermassive black hole, where matter is compressed upon falling into the hole and heated to extremely high temperatures.
B.A very rapidly rotating core of matter, where friction between it and the surrounding matter causes tremendous heat and energy output.
C.There is no central "engine" in these sources. Their high gravity has focused radiation from many sources beyond them by gravitational lensing and they thus appear to be very bright.
D.a steady series of supernova explosions, the late evolutionary stages of massive stars.

62. Where are we?
A.Near the edge of an expanding universe, as shown by the microwave radiation coming to us from the edge.
B.At the exact center of an expanding universe, as shown by the universal expansion away from us in all directions.
C.Somewhere in an expanding universe, but not in any special part of it.
D.Near, although probably not right at, the center of the universe, as shown by the fact that the edge is so far away.

63. The further away a galaxy is, the more its light is redshifted, as seen by us on the Earth. This relationship between redshift and distance is caused by
A.the Doppler shift of light leaving a moving object. More distant galaxies are moving faster through space, so their light is more strongly Doppler-shifted (redshifted).
B.the expansion of space itself, which stretches the wavelength of the photon. The longer the time that the photon has traveled, the more space has expanded and therefore the more the photon has been redshifted.
C.the gravitational redshift. Photons leaving a more distant galaxy have traveled further through the galaxy's gravitational field, so they have lost more energy and are more redshifted.
D.energy losses. The universe does not really expand; photons simply lose energy (wavelength lengthens) as they travel. Photons from more distant galaxies have traveled further and so are more redshifted.

64. For any object moving uniformly, velocity = distance/time. If so, in the Hubble relationship for the expansion of the universe, v = H0r, what is the significance of the constant 1/H0?
A.It is merely a constant of proportionality, to allow for the different units in v and r.
B.It represents the time since the expansion began, or the age of the universe.
C.It is the inverse of the velocity that the object would have at a standard distance of 10 parsecs.
D.It represents the average spacing between objects in the universe at the present time.

65. The cosmic background radiation is
A.the beam of atomic nuclei known as cosmic rays that continuously rain down upon the Earth from all directions in space.
B.the radio noise generated by Earth-bound transmitters, spreading out into space since about 1920.
C.low intensity radio noise, with a 3 K blackbody temperature, almost uniform in intensity in all directions.
D.the flux of visible radiation in empty space, contributed by all visible stars in the universe.

66. The cosmic microwave background is found to be extremely uniform throughout space, with only very small fluctuations in intensity. The event that produced this remarkable smoothness in the early universe was
A.the start of the production of matter in the universe, which smoothed out the irregularities in space.
B.the fact that the Big Bang occurred everywhere in space at the same time.
C.a sudden but brief period of rapid expansion of the universe during the general expansion of the early universe.
D.Heisenberg's uncertainty principle, which prevented the concentration of radiant energy in localized volumes of space.

67. In what way does the study of the collisions of very high speed nuclear particles with other matter at particle accelerator laboratories help in the understanding of the early universe?
A.Collisions in nuclear accelerator laboratories produce large numbers of neutrinos and hence mimic the conditions that were thought to exist in the early universe, where neutrinos occupied most of the space.
B.Motion of particles in circular orbits around the original black hole produced by the Big Bang were similar to the particle motions in an accelerator.
C.Nuclear accelerators generate enormous quantities of microwaves similar to those that existed in the early universe, thus allowing the study of the interaction of microwaves with matter.
D.The temperature of the early universe was extremely high, such that mutual collisions of particles occurred at energies equivalent to those in nuclear particle accelerators.

68. Why would we expect the rate of expansion of the universe to be slowing down?
A.The greater the distance between two objects (such as galaxies or superclusters), the harder it is to push them further apart.
B.Galaxies feel a kind of friction as they move through space, and this slows them down.
C.The gravitational pull of all objects in the universe on each would lead to slow-down.
D.All expansions after explosions just naturally slow down with time.

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