Download Name Physics 130 Astronomy Exam 2 August 2, 2004 Multiple Choice

Name _____________________________________
Physics 130
Astronomy
Exam 2
August 2, 2004
Multiple Choice:
1. _____ When visible light passes through a prism of glass, which wavelengths of light are deflected
most by the glass?
a.) Intermediate wavelengths, the green color
b.) The longer wavelengths
c.) The shorter wavelengths
d.) All wavelengths are deviated by the same amount
2. _____ In what way does a photon of blue light NOT differ from a photon of yellow light, in a
vacuum?
a.) Speed
b.) Energy
c.) Color
d.) Wavelength
3. _____ In a radio transmitter (such as that used by a radio or TV station), when the frequency of the
signals is increased.
a.) The wavelength is decreased
b.) The speed of the transmission of the waves is increased
c.) The wavelength remains constant
d.) The wavelength and speed of transmission both increase
4. _____ Refraction is
a.) the bending of light as it enters a transparent material at an angle less than perpendicular to the
surface of the material
b.) the change in the direction of light when it bounces off a smooth surface
c.) the bending of light around the sharp edge of an obstacle
d.) the change in the color of light when it enters a transparent but colored material such as glass.
5.
_____ Which of the following characteristics of an astronomical telescope is the most important for
determining the angular resolution?
a.) The diameter of the objective lens or mirror
b.) The magnifying power of the telescope
c.) The focal length of the objective lens or mirror
d.) The focal length of the eyepiece
6.
_____ What does the word “seeing” mean to an astronomer using a telescope?
a.) The combined effect of aberrations in the telescope, particularly chromatic and spherical
aberration.
b.) The twinkling and blurring of the image due to air currents in the Earth’s atmosphere.
c.) The amount of haze or thin cloud in the atmosphere, that affects the brightness of the telescope
image.
d.) The effect of the wind, that can cause the telescope to vibrate blurring the image.
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7.
_____ An ideal “blackbody” in physics and astronomy is an object which
a.) emits only infrared light, and hence appears black to the eye
b.) does not emit or reflect any radiation
c.) reflects and emits radiation in a manner which is completely determined by its temperature.
d.) reflects and emits light with the same intensity at all wavelengths.
8.
_____ A piece of iron is heated from 400 to 800 K (127C° to 527°C). The total energy emitted per
second by this iron will increase by a factor of
a.) 16
b.) 296.5
c.) 4
d.) 2
9.
_____ The chemical makeup of a star’s surface is usually inferred
a.) by spectroscopy of the light emitted by the star
b.) by taking a sample of that surface with a space probe
c.) by theoretical methods, considering evolution of the star
d.) by measuring the chemical elements present in the solar wind.
10. _____ The spectrum of sunlight, when spread out by a spectrograph, has what characteristic
appearance?
a.) A series of separate emission lines, characteristic of many elements, which overlap in certain
regions of the spectrum to produce short sections of continuous color.
b.) A continuous band of color, crossed by innumerable emission lines
c.) A continuous band of color, crossed by innumerable dark absorption lines.
d.) A continuous and uniform band of color from violet to deep red.
11. _____ The proton, the nucleus of the hydrogen atom, has a mass which exceeds that of the electron
by approximately what factor?
a.) 100 times
b.) 2000 times
c.) 2 times
d.) 104 times
12. _____ How many electrons surround the nucleus of a neutral atom of Iron, the 26th element in the
periodic table?
a.) 27
b.) 57
c.) 25
d.) 26
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13. _____ According to the Doppler effect
a.) the wavelength of light is shifted to shorter wavelength if the source of light is moving toward
you.
b.) the wavelength of peak emission of light from a source changes as the temperature of the source
changes.
c.) the wavelength of light is shifted to a longer wavelength if the source of the light is moving
toward you.
d.) spectral lines are split into two or more wavelengths when the source of the light is in a strong
magnetic field.
14. _____ Granulation on the surface of the Sun is caused by
a.) magnetic field disturbances above the solar surface.
b.) convective currents carrying heat from beneath the surface.
c.) nuclear fusion processes occurring just below the surface.
d.) differential rotation of the Sun.
15. _____ The major feature which distinguishes a sunspot from other regions on the sun is
a.) a much brighter emission of light from it.
b.) its very powerful magnetic field.
c.) a coronal hole existing above it.
d.) faster rotation around the Sun’s axis than neighboring regions.
16. _____ A positron is
a.) a hydrogen nucleus.
b.) a positively charged electron.
c.) a charged neutron.
d.) a positively charged neutrino.
17. _____ Energy is transported from the center of the Sun to the surface by
a.) mostly convection, radiation only in the outer layers
b.) convection in the thermonuclear core, radiation everywhere else.
c.) mostly radiation; convection only in the outer layers.
d.) radiation in the thermonuclear core; convection everywhere else.
18. _____ Stellar parallax is
a.) the circular or elliptical motion of a star in a binary system, as the two stars orbit around each
other.
b.) the apparent shift that we see in the position of a nearly star as we orbit the Sun.
c.) the difference between the apparent magnitude and the absolute magnitude of a star.
d.) the apparent change in the distance to a star if its light is dimmed by passing through interstellar
clouds.
19. _____ A particular star is 20 pc away from the Earth. What is the angle of parallax for this star?
a.) 6 arcsec
b.) 2 arcsec
c.) 0.02 arcsec
d.) 0.05 arcsec
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20. _____ Suppose that two identical stars (having the same total light output) are located such that star
A is at a distance of 5 pc and star B is at a distance of 25 pc. How will star B appear, compared to star
A?
a.) Star B will be ½.2 as bright as star A.
b.) Star B will be 1/20 as bright as star A.
c.) Star B will be 1/25 as bright as star A.
d.) Star B will be 1/5 as bright as star A.
21. _____ Which of the following sequences of stellar spectral classifications is in correct order of
INCREASING temperature?
a.) K, M, G, F, A, B, O
b.) M, K, G, F, A, B, O
c.) O, B, A. F, G, K, M
d.) A, B, F, G, K, M, O
22. _____ The Hertzsprung-Russell diagram is a plot of
a.) apparent brightness against intrinsic brightness of a group of stars
b.) apparent brightness against distance for stars near to the Sun.
c.) absolute magnitude (or intrinsic brightness) against temperature of a group of stars.
d.) luminosity against mass of a group of stars.
23. _____ What is the only way to measure the mass of a star accurately?
a.) Measure its spectral type and luminosity class, then use the HR diagram.
b.) Measure its distance using trigonometric parallax and its brightness using photometry.
c.) Measure its gravitational effect on another object.
d.) It is not possible to measure the mass of a star.
24. _____ A particular star in a binary star system orbits the other in an elliptical orbit with a semimajor
axis of 3AU and a period of 5 years. What is the sum of the masses of the two stars in the system?
a.) 1.1 solar masses
b.) 0.07 solar masses
c.) 13.9 solar masses
d.) 0.9 solar masses
25. _____ Which are the two most abundant elements in the universe?
a.) Nitrogen and oxygen
b.) Hydrogen and helium
c.) Hydrogen and oxygen
d.) Hydrogen and carbon
26. _____ In which part of the electromagnetic spectrum are molecules most easily detected?
a.) Visible light
b.) Ultraviolet light
c.) Radio waves
d.) X-rays
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27. _____ How do massive stars normally end their lives?
a.) They collapse and become black holes.
b.) We don’t know, since their lifetimes are longer than the age of the universe.
c.) They explode
d.) They gradually shrink to the size of the Earth.
28. _____ The major source of energy in the pre-main-sequence life of the Sun was
a.) nuclear fusion.
b.) gravitational
c.) nuclear fusion
d.) burning of carbon atoms.
29. _____ The smallest mass which a main sequence star can have is about 0.08 solar mass. The reason
for this is that
a.) thermonuclear reactions begin so suddenly in stars of less than 0.08 solar mass that the star is
disrupted by an explosion.
b.) the temperature in a contracting protostar of less than 0.08 solar masses does not get high enough
for nuclear reactions to start.
c.) protostars cannot form with masses less than 0.08 solar mass.
d.) protostars of less than 0.08 solar masses are not massive enough to contract.
30. _____ An object which is too massive to be a planet but not massive enough to be a star is called
a.) a red dwarf
b.) a white dwarf
c.) a T Tauri star
d.) a brown dwarf
31. _____ all stars on the main sequence
a.) generate energy by hydrogen fusion in their centers.
b.) are changing slowly in size, by gravitational contraction.
c.) have approximately the same age, to within a few million years.
d.) are at a late stage of evolution after the red giant stage.
32. _____ What is the most important quantity on which the lifetime of a star depends?
a.) The star’s speed of rotation.
b.) The mass of the star.
c.) The abundant of heavy elements in the star.
d.) Its surface temperature.
33. _____ What makes a red giant so large?
a.) Red giants are rapid rotators, and centrifugal force pushes the surface of the star outwards.
b.) The star has many more times the mass of the Sun.
c.) The hydrogen-burning shell is heating the outer portions of the star and making the star expand.
d.) The helium-rich core has expanded, pushing the outer layers of the star outwards.
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34. _____ During helium burning in a star’s later life, the chemical element produced by the combination
of helium nuclei is
a.) beryllium, 8Be
b.) carbon, 12C
c.) the light isotope of helium, 3He
d.) Heavy hydrogen, 2H
35. _____ Cepheid stars are
a.) members of binary systems, in which one star periodically eclipses the other.
b.) Stars at an early stage in stellar evolution, pre-main-sequence.
c.) White dwarf stars, late in their evolutionary life
d.) Giant stars that pulsate in brightness, size, and temperature.
36. _____ A planetary nebula is
a.) a disk-shaped nebula of gas and dust, photographed around a relatively young star, from which
planets will eventually form.
b.) A contracting spherical cloud of gas surrounding a newly formed star in which planets are
forming.
c.) The nebula caused by the supernova explosion of a massive star.
d.) An expanding gas shell surrounding a hot white dwarf star.
37. _____ Thermonuclear reactions release energy because
a.) the product (ash) nucleus is more tightly bound than the original (fuel) nucleus.
b.) the product (ash) nucleus is less tightly bound than the original (fuel) nucleus.
c.) the product (ash) nucleus is moving faster than the original (fuel) nucleus, and this excess kinetic
energy shows up as heat.
d.) The product (ash) nucleus contains fewer protons than the original (fuel) nucleus, since these
protons have been converted into energy.
38. _____ The core collapse phase at the end of the life of a massive star is triggered when
a.) nuclear fusion has produced a significant amount of iron in its core
b.) the density reaches the threshold for electron degeneracy pressure to become important.
c.) The helium flash and thermal pulses have expelled the star’s envelope.
d.) The core becomes as dense as an atomic nucleus.
39. _____ The neutrino is
a.) another name for an anti-neutron, the anti-particle of the neutron, very difficult to detect.
b.) an elusive, subatomic particle, having no (or very small) mass, very difficult to detect.
c.) a heavy nuclear particle, easily detected.
d.) another name for an anti-electron or positron.
40. _____ The Crab Nebula is a nearby example of what type of physical phenomenon?
a.) The remnant of a supernova explosion.
b.) A gas and dust cloud, the formative region for new stars.
c.) A planetary nebula, a shell of gas leaving an old star.
d.) A spiral galaxy, a collection of 100 billion stars.
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True or False:
41. _____ Stars on the upper main sequence evolve away from the main sequence before stars on the
lower main sequence.
42. _____ All stars in a star cluster are assumed to have the same mass.
43. _____ The source of energy in solar-type stars is the proton-proton cycle.
44. _____ The location of a star on the main sequence depends on its initial radius..
45. _____ Stars spend most of their existence on the main sequence.
46. ______ If the core of a star generates more energy than the star can radiate, the star will heat and
expand.
47. ______Because of the high pressure and density in the core of a star, the center is a solid.
48. _____ All massive stars we observe must be older than the Sun.
49. ______The stars with the strongest hydrogen absorption lines belong to spectral class A.
50. ______Ion is simply another word for atom.
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