Download Test 1, Feb. 2, 2016 - Brock physics

Brock University
Number of pages: 9
Number of Students: 500
Number of hours: 50 min
Instructor: B.Mitrović
Test 1, February, 2016
Course: ASTR 1P02
Date of Examination: February 2, 2016
Time of Examination: 17:00–17:50
1. A dark nebula emits energy mostly in the form of
(a) gamma-ray radiation.
(b) X-ray radiation.
(c) UV radiation
(d) infrared radiation.
2. The blue colour of a nebula arises because
(a) the red light is scattered away out of its path by the dust in the nebula.
(b) hot hydrogen in the nebula emits blue light.
(c) the blue light is scattered most efficiently by the dust in the nebula.
(d) the blue light is absorbed by the dust and gas in the nebula.
3. A nebula which produces light by fluorescence is called
(a) reflection
(b) planetary
(c) emission
(d) [None of the above.]
4. A bluish nebula is called
nebula.
(a) reflection
(b) planetary
(c) emission
(d) [None of the above.]
5. The spin rate of a pulsar
(a) increases over time.
(b) decreases over time.
(c) does not change in time.
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nebula.
Course: ASTR1P02
Date: February 2, 2016
page 2 of 9 pages
6. The wavelength of a source of light approaching the event horizon of a black hole is
(a) blueshifted.
(b) redshifted.
(c) unchanged.
7. About one quarter of material in a nebula is
(a) dust.
(b) hydrogen.
(c) helium.
8. Which one of these stars spends more time in protostar stage?
(a) 1 solar mass star.
(b) 10 solar mass star.
9. The stronger is the force of gravity on a clock, the faster it runs.
(a) True.
(b) False.
10. During the protostar stage, a star derives its energy from
(a) hydrogen fusion.
(b) gravitational contraction.
11. A protostar with mass 0.3 solar mass will become
(a) a brown dwarf.
(b) a red dwarf.
12. Stars like the Sun do not form iron cores during their evolution because
(a) their strong magnetic fields keep their iron in their atmospheres.
(b) there is no iron to begin with that could sink to the core.
(c) their cores never get hot enough to form iron by nucleosynthesis.
(d) [Stars like the Sun do form iron cores.]
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Course: ASTR1P02
Date: February 2, 2016
page 2 of 9 pages
13. Which of the following sequences describes the evolution of the Sun from young to old?
(a) Protostar, main-sequence, yellow giant, red giant, black hole.
(b) Protostar, main-sequence, yellow giant, red giant, neutron star.
(c) Protostar, main-sequence, red giant, yellow giant, red giant, white dwarf.
(d) [None of the above.]
14. The non-fusing dead core of a star is supported against its collapse by
(a) its own gravity.
(b) radiation pressure.
(c) degenerate electrons.
(d) its magnetic field.
15. The main-sequence stage of the Sun is estimated to be
long.
(a) 10 million years
(b) 100 million years
(c) 1 billion years
(d) 10 billion years
16. Once the hydrogen in the Sun’s core is fused into helium, further fusion of hydrogen into
helium will go on in
(a) its atmosphere.
(b) photosphere.
(c) a shell surrounding the helium core.
17. When a medium-mass main-sequence star exhausts its core hydrogen fuel supply:
(a) the entire star shrinks in size.
(b) the core shrinks while the rest of the star expands.
(c) the core immediately begins to fuse its helium into carbon.
(d) the star becomes a neutron star.
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Course: ASTR1P02
Date: February 2, 2016
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18. The helium burning into carbon in the core of a medium mass star proceeds via
(a) proton-proton chain.
(b) CNO-cycle.
(c) triple alpha-process.
19. Planetary nebula is
(a) a glowing shell of material ejected by a dying medium-mass star.
(b) a supernova remnant.
(c) a nebula in which planets form around a star.
(d) [None of the above.]
20. If the mass of an object composed of degenerate material increases, its radius decreases.
(a) True.
(b) False.
21. White dwarfs with masses in excess of two solar masses have been observed.
(a) True.
(b) False.
22. Which of these white dwarfs has larger radius?
(a) One solar mass white dwarf.
(b) Half a solar mass white dwarf.
23. A white dwarf is composed of
(a) helium.
(b) iron.
(c) carbon nuclei, some oxygen nuclei and degenerate electrons.
(d) [None of the above.]
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Course: ASTR1P02
Date: February 2, 2016
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24. The gravitational collapse of a high-density white dwarf is prevented by
(a) the rapid spin of a white dwarf.
(b) the pressure created by degenerate electrons.
(c) thermal pressure created by carbon nuclei.
(d) the pressure created by degenerate carbon nuclei
25. The density of a white dwarf is about
(a) 1011 kilograms per centimeter cubed (i.e., equal to the typical density of an atomic
nucleus.
(b) 1000 kilograms per centimeter cubed.
(c) 10 grams per centimeter cubed (i.e., equal to typical metallic density).
(d) 1 gram per centimeter cubed (i.e., equal to the density of water).
26. There are hydrogen spectral lines in the spectrum of Type Ia supernova.
(a) True.
(b) False.
27. Chandrasekhar’s limit is
(a) the maximum radius of a red giant.
(b) the radius within which an object must shrink to become a black hole.
(c) the maximum mass of a body composed of degenerate matter.
(d) the minimum mass of a body composed of degenerate matter.
28. Type Ia supernova occurs
(a) when a large mass star explodes.
(b) in a white dwarf-star binary system when the mass transfer pushes the mass of the
white dwarf above the maximum value it can have.
(c) in a pulsar-star binary system when the mass transfer pushes the mass of the pulsar
above the maximum value it can have.
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Course: ASTR1P02
Date: February 2, 2016
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29. The maximum mass that a white dwarf can have is
(a) 0.14 solar masses.
(b) 1.4 solar masses.
(c) 14 solar masses.
(d) [The statement is wrong. A white dwarf can have any mass.]
30. Which of the following nuclei has the lowest binding energy per nucleon?
(a) The nucleus of helium.
(b) The nucleus of carbon.
(c) The nucleus of iron.
31. Which is the heaviest element that can be obtained through nuclear fusion of the lighter
ones with a release of energy?
(a) Gold.
(b) Iron.
(c) Silicon.
(d) Carbon.
32. There are hydrogen spectral lines in the spectrum of Type II supernova.
(a) True.
(b) False.
33. Which of these fusion reactions in a high-mass star lasts the shortest period of time?
(a) The fusion of hydrogen into helium.
(b) The fusion of helium into carbon.
(c) The fusion of silicon into iron.
34. Why does the core of a high mass star collapse?
(a) The iron core’s mass is too small to support the rest of the star.
(b) Because the iron core transforms from solid to liquid.
(c) Because the iron core’s mass becomes so big that degenerate electrons cannot sustain the pressure and the electrons combine with protons in the nuclei to produce
neutrons and neutrinos.
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Course: ASTR1F00
Date: February 2, 2016
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35. Type II supernova occurs
(a) in a white dwarf-star binary system when the mass transfer pushes the mass of the
white dwarf above the maximum value it can have.
(b) when a regular star is swallowed by a black hole.
(c) when a large mass stars explodes.
(d) in a pulsar-star binary system when the mass transfer pushes the mass of the pulsar
above the maximum value it can have.
36. Type II supernovae are important because
(a) all of a star’s hydrogen is returned to the interstellar medium.
(b) the elements heavier than iron are synthesized.
(c) the resulting burst of neutrinos keeps the galaxy from collapsing.
(d) they produce helium from hydrogen.
37. Most of supernova 1987A energy output (luminosity) was in the form of neutrinos.
(a) True.
(b) False.
38. Crab nebula is a
(a) giant molecular cluster.
(b) planetary nebula.
(c) supernova remnant.
39. A pulsar is
(a) a fast spinning neutron star.
(b) a pulsating yellow giant star.
(c) the pulsating iron core of a giant star.
40. What causes the radio pulses of a pulsar?
(a) The star’s orbiting companion periodically eclipses the radio waves emitted by the
main star.
(b) As the star spins, beams of radiation from it sweep through space. If one of these
beams points towards the Earth, we observe a pulse.
(c) The star vibrates.
(d) The star undergoes nuclear explosions that generate radio emissions.
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Course: ASTR1P02
Date: February 2, 2016
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41. According to the General Theory of Relativity, mass/energy curves spacetime.
(a) True.
(b) False.
42. In order to detect a black hole one looks for
(a) a spot into which stars and their planets fall.
(b) a binary system where a companion star is not visible but has a mass greater than
3 solar masses and is an intense X-ray source.
(c) intense source of visible light.
(d) the accompanying white hole.
43. Which of these stars spends the longest time as a main sequence star?
(a) 0.5 solar mass star.
(b) 1 solar mass star.
(c) 15 solar mass star.
(d) [No statement can be made.]
44. The current luminosity of the Sun is
(a) smaller than when it was formed 4.6 billion years ago.
(b) the same as when it was formed 4.6 billion years ago.
(c) larger than when it was formed 4.6 billion years ago.
(d) [No statement can be made.]
45. Which of these fusion reactions in a high-mass star creates most energy per nuclear
reaction?
(a) The fusion of hydrogen into helium.
(b) The fusion of helium into carbon.
(c) The fusion of silicon into iron.
(d) [No statement can be made.]
46. The pressure of degenerate electrons increases with temperature.
(a) True.
(b) False.
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Course: ASTR1P02
Date: February 2, 2016
47. Sirius B is
(a) a main sequence star.
(b) a pulsar.
(c) a white dwarf.
(d) a planetary nebula.
(e) a supernova remnant.
48. A star of 5 solar mass fuses hydrogen into helium via
(a) proton-proton chain.
(b) triple alpha process.
(c) CNO cycle.
49. A star of 0.5 solar mass fuses hydrogen into helium via
(a) proton-proton chain.
(b) triple alpha process.
(c) CNO cycle.
50. White dwarfs will stop emitting light in a distant future.
(a) True.
(b) False.
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