Astronomy Chapter 5

2) If a material is highly opaque, then it

A) reflects most light.

B) absorbs most light.

C) transmits most light.

D) scatters most light.

E) emits most light.

B

3) When light reflects off an object, what is the relation between the angle of incidence and the angle of reflection?

A) angle of incidence = angle of reflection

B) angle of incidence + angle of reflection = 90°

C) angle of incidence + angle of reflection = 180°

D) angle of incidence - angle of reflection = 90°

E) It depends on the material that the light reflects off.

A

4) If a material is transparent, then it

A) reflects light well.

B) absorbs light well.

C) transmits light well.

D) scatters light well.

E) emits light well.

C

5) Grass (that is healthy) looks green because

A) it emits green light and absorbs other colors.

B) it absorbs green light and emits other colors.

C) it transmits green light and emits other colors.

D) it reflects green light and absorbs other colors.

D

6) Everything looks red through a red filter because

A) the filter emits red light and absorbs other colors.

B) the filter absorbs red light and emits other colors.

C) the filter transmits red light and absorbs other colors.

D) the filter reflects red light and transmits other colors.

C

7) Which of the following cannot be described by a field?

A) gravitational forces

B) electrical forces

C) magnetic forces

D) radiation pressure

D

8) The frequency of a wave is

A) the number of peaks passing by any point each second.

B) measured in cycles per second.

C) measured in hertz (Hz).

D) equal to the speed of the wave divided by the wavelength of the wave.

E) all of the above

E

9) The wavelength of a wave is

A) how strong the wave is.

B) the distance between a peak of the wave and the next trough.

C) the distance between two adjacent peaks of the wave.

D) the distance between where the wave is emitted and where it is absorbed.

E) equal to the speed of the wave times the wave's frequency.

C

10) How are wavelength, frequency, and energy related for photons of light?

A) Longer wavelength means lower frequency and lower energy.

B) Longer wavelength means higher frequency and lower energy.

C) Longer wavelength means higher frequency and higher energy.

D) Longer wavelength means lower frequency and higher energy.

E) There is no simple relationship because different photons travel at different speeds.

A

11) From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?

A) infrared, visible light, ultraviolet, X rays, gamma rays, radio

B) radio, infrared, visible light, ultraviolet, X rays, gamma rays

C) visible light, infrared, X rays, ultraviolet, gamma rays, radio

D) gamma rays, X rays, visible light, ultraviolet, infrared, radio

E) radio, X rays, visible light, ultraviolet, infrared, gamma rays

B

12) From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

A) infrared, visible light, ultraviolet, X rays, gamma rays, radio

B) radio, infrared, visible light, ultraviolet, X rays, gamma rays

C) visible light, infrared, X rays, ultraviolet, gamma rays, radio

D) gamma rays, X rays, ultraviolet, visible light, infrared, radio

E) gamma rays, X rays, visible light, ultraviolet, infrared, radio

D

13) Which of the following statements about X rays and radio waves is not true?

A) X rays have shorter wavelengths than radio waves.

B) X rays and radio waves are both forms of light, or electromagnetic radiation.

C) X rays have higher frequency than radio waves.

D) X rays have higher energy than radio waves.

E) X rays travel through space faster than radio waves.

E

14) Which of the following statements about X rays and radio waves is not true?

A) Neither X rays nor radio waves can penetrate the earth's atmosphere.

B) X rays have shorter wavelengths than radio waves.

C) X rays and radio waves are both forms of light, or electromagnetic radiation.

D) X rays have higher frequency than radio waves.

E) X rays have higher energy than radio waves.

A

15) We can see each other in the classroom right now because we

A) emit thermal radiation.

B) emit visible light.

C) emit infrared light.

D) reflect visible light.

E) reflect infrared light.

D

16) Without telescopes or other aid, we can look up and see the Moon in the night sky because it

A) emits visible light.

B) emits thermal radiation.

C) reflects infrared light.

D) reflects visible light.

E) glows through radioactive decay.

D

17) How many atoms fit across the period at the end of this sentence?

A) hundreds

B) thousands

C) millions

D) billions

E) more than you could count in a lifetime

C

18) What is a compound?

A) a group of molecules

B) a molecule containing hydrogen

C) a molecule containing two or more elements

D) an ionized molecule

E) a molecule containing carbon

C

19) Compared to the volume of its nucleus, the volume of an atom is about

A) the same.

B) a thousand times greater.

C) a million times greater.

D) a billion times greater.

E) a trillion times greater.

E

21) Which of the following statements about electrical charge is true?

A) Two negative charges will attract each other.

B) Two positive charges will attract each other.

C) A positive charge and a negative charge will repel each other.

D) A positive charge and a negative charge will attract each other.

D

22) Which of the following statements about electrons is not true?

A) Electrons orbit the nucleus rather like planets orbiting the Sun.

B) Within an atom, an electron can have only particular energies.

C) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.

D) An electron has a negative electrical charge.

E) Electrons have very little mass compared to protons or neutrons.

A

23) Suppose you built a scale-model atom in which the nucleus was the size of a tennis ball. About how far would the cloud of electrons extend?

A) several centimeters

B) a few meters

C) a few tens of meters

D) several kilometers

E) to the Sun

D

29) At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?

A) a gas of rapidly moving molecules

B) a plasma consisting of positively charged ions and free electrons

C) a gas consisting of individual, neutral atoms, but no molecules

D) a plasma consisting of rapidly moving, neutral atoms

E) none of the above (At these extremely high temperatures, matter cannot exist.)

B

30) Sublimation is the process in which

A) molecules go from the solid phase to the liquid phase.

B) molecules go from the liquid phase to the gas phase.

C) molecules go from the solid phase to the gas phase.

D) electrons are stripped from atoms.

E) electrons are captured by ions.

C

31) Dissociation is the process in which

A) the bonds between atoms in a molecule are broken.

B) a molecule goes from the solid phase to the gas phase.

C) the bonds between electrons around an atomic nucleus are broken.

D) an element changes into another form.

E) an electron is shared between atomic nuclei.

A

32) When an atom loses an electron, it becomes

A) sublimated.

B) dissociated.

C) ionized.

D) an isotope.

E) a plasma.

C

33) An atom in an excited state contains more of what type of energy than the same atom in the ground state?

A) mass-energy

B) kinetic energy

C) thermal energy

D) gravitational potential energy

E) electric potential energy

E

34) When an atom absorbs a photon containing energy, any of the following can happen except which?

A) The atom becomes excited.

B) The atom is ionized.

C) An electron moves from an upper energy level to a lower one.

D) An electron moves from a lower energy level to an upper one.

C

35) The loss of an electron from a neutral helium atom results in

A) neutral hydrogen.

B) ionized hydrogen.

C) ionized helium.

D) neutral deuterium.

E) ionized deuterium.

C

36) An electron-volt is

A) the charge of one electron.

B) the energy of one electron.

C) the energy jump between the first and second energy levels of hydrogen.

D) an amount of energy much smaller than a joule.

E) an amount of energy much larger than a joule.

D

37) The study of energy levels in atoms is called

A) special relativity.

B) general relativity.

C) quantum mechanics.

D) classical mechanics.

E) particle physics.

C

38) How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?

A) It loses kinetic energy.

B) It releases a photon equal in energy to its own energy drop.

C) It absorbs a photon equal in energy to its own energy drop.

D) It loses gravitational potential energy.

E) It exchanges gravitational potential energy for kinetic energy.

B

39) If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces

A) thermal radiation.

B) an absorption line spectrum.

C) an emission line spectrum.

D) X rays.

E) radio waves.

C

40) When an electron in an atom goes from a higher energy state to a lower energy state, the atom

A) emits a photon of a specific frequency.

B) absorbs a photon of a specific frequency.

C) absorbs several photons of a specific frequency.

D) can emit a photon of any frequency.

E) can absorb a photon of any frequency.

A

41) When white light passes through a cool cloud of gas, we see

A) visible light.

B) infrared light.

C) thermal radiation.

D) an absorption line spectrum.

E) an emission line spectrum.

D

42) Spectra from neutral atoms compared with spectra from ionized atoms of the same element

A) are the same.

B) are slightly redshifted.

C) are slightly blueshifted.

D) have different sets of spectral lines.

E) have the same sets of spectral lines but different widths for those lines.

D

43) Which of the following objects is not a close approximation of a thermal emitter?

A) hot, thin gas

B) a star

C) a filament in a light bulb

D) you

E) a planet

A

44) Thermal radiation is defined as

A) radiation produced by a hot object.

B) radiation in the infrared part of the spectrum.

C) radiation that depends only on the emitting object's temperature.

D) radiation in the form of emission lines from an object.

E) radiation that is felt as heat.

C

45) A perfectly opaque object that absorbs all radiation and reemits the absorbed energy as thermal radiation is

A) a hot, dense cloud of gas.

B) a cold, dense cloud of gas.

C) an infrared radiation emitter.

D) a thermal emitter.

E) transparent.

D

46) Which of the following statements about thermal radiation is always true?

A) A hot object emits more X rays than a cool object.

B) A hot object emits more radio waves than a cool object.

C) A hot object emits more total radiation than a cool object.

D) A hot object emits more total radiation per unit surface area than a cool object.

E) A hot object emits less total radiation than a cool object.

D

47) Which of the following statements about thermal radiation is always true?

A) A hot object emits photons with a longer wavelength than a cool object.

B) A hot object emits photons with a higher average energy than a cool object.

C) A hot object emits more radio waves than a cool object.

D) A hot object emits more X rays than a cool object.

B

49) A gas heated to millions of degrees would emit

A) mostly radio waves.

B) mostly X rays.

C) mostly ultraviolet light.

D) an equal amount of all wavelengths of light.

E) no light, because it is too hot.

B

50) We can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one?

A) The peak of the star's thermal emission tells us its temperature: Hotter stars peak at shorter (bluer) wavelengths.

B) The total amount of light in the spectrum tells us the star's radius.

C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.

D) We can look at Doppler shifts of spectral lines to determine the star's speed toward or away from us.

B

51) The spectra of most galaxies show redshifts. This means that their spectral lines

A) always are in the red part of the visible spectrum.

B) have wavelengths that are longer than normal.

C) have wavelengths that are shorter than normal.

D) have a higher intensity in the red part of the spectrum.

E) have normal wavelengths, but absorption of light makes them appear red.

B

54) How does the spectrum of a molecule differ from the spectrum of an atom?

A) A molecule does not have spectral lines due to electrons changing energy levels.

B) A molecule has additional spectral lines due to changes in its rotational and vibrational energies.

C) Molecules only have spectral lines at ultraviolet wavelengths.

D) Most atoms only have spectral lines at infrared wavelengths.

E) An atom has a wider range of spectral lines than molecules.

B

55) You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?

A) The galaxy is moving away from you.

B) The galaxy is moving toward you.

C) The galaxy has very weak gravity.

D) The galaxy is made purely of hydrogen.

E) The composition of the galaxy is changing.

A

56) If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?

A) The one with the large redshift is moving toward us faster than the one with the small redshift.

B) The one with the large redshift is moving away from us, and the one with the small redshift is moving toward us.

C) The one with the large redshift is moving away from us faster than the one with the small redshift.

D) The one with the large redshift is hotter and therefore is putting out more radiation.

E) The one with the large redshift is redder than the other one.

C

57) If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

A) The planet is actually two bodies, one moving toward us, the other away from us.

B) The planet is in the process of falling apart.

C) The planet is in the process of formation.

D) The planet is rotating.

E) The planet's surface is very different from one side to the other.

D

58) Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

A) The red star is more massive than the blue star.

B) The blue star is more massive than the red star.

C) The blue star is farther away than the red star.

D) The blue star has a hotter surface temperature than the red star.

E) The red star has a hotter surface temperature than the blue star.

D

59) You observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two?

A) There is no difference.

B) The line in the faster rotating star is blueshifted.

C) The line in the faster rotating star is redshifted.

D) The line in the faster rotating star is broader.

E) The line in the faster rotating star is narrower.

D

7) Which forms of light are lower in energy and frequency than the light that our eyes can see?

A) infrared and radio

B) ultraviolet and X rays

C) visible light

D) infrared and ultraviolet

A

8) If we say that a material is opaque to ultraviolet light, we mean that it

A) absorbs ultraviolet light.

B) emits ultraviolet light.

C) transmits ultraviolet light.

D) reflects ultraviolet light.

A

9) Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?

A) a few meters

B) several centimeters

C) several kilometers

D) to the Sun

C

13) Sublimation is the process in which

A) molecules go from the solid phase to the liquid phase.

B) molecules go from the liquid phase to the gas phase.

C) molecules go directly from the solid phase to the gas phase.

D) electrons are stripped from atoms.

C

14) Which of the following transitions within an atom is not possible?

A) An electron begins in an excited state and then gains enough energy to jump to the ground state.

B) An electron begins in the ground state and then gains enough energy to jump to an excited state.

C) An electron begins in the ground state and then gains enough energy to become ionized.

D) An electron begins in an excited state and then gains enough energy to become ionized.

A

16) Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?

A) An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.

B) An emission line spectrum consists of a long bright line, while an absorption line spectrum consists of a long dark line.

C) The only way to decide is to make a graph of the intensity of the light at every wavelength, and then analyze the graph carefully.

D) The emission line spectrum is produced by electrons jumping up in energy level, while the absorption line spectrum is produced by electrons jumping down in energy level.

A

17) Thermal radiation is defined as

A) radiation with a spectrum whose shape depends only on the temperature of the emitting object.

B) radiation produced by an extremely hot object.

C) radiation that is felt as heat.

D) radiation in the form of emission lines from an object.

A

18) According to the laws of thermal radiation, hotter objects emit photons with

A) a lower average frequency.

B) a shorter average wavelength.

C) a lower average energy.

D) a higher average speed.

B

19) Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

A) The peak energy of the star's thermal radiation.

B) The Doppler shift of the star's spectrum.

C) The wavelengths of spectral lines in the star's spectrum.

D) Whether the star's spectrum has more emission lines or more absorption lines.

C

20) The spectra of most galaxies show redshifts. This means that their spectral lines

A) have wavelengths that are longer than normal.

B) always are in the red part of the visible spectrum.

C) have wavelengths that are shorter than normal.

D) have a higher intensity in the red part of the spectrum.

A

21) You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?

A) The galaxy is moving away from you.

B) The galaxy is moving towards you.

C) The galaxy has very weak gravity.

D) The galaxy is made purely of hydrogen.

A

2) Which of the following statements is true of green grass?

A) It absorbs red light and emits green light.

B) It absorbs red light and reflects green light.

C) It transmits all colors of light except green.

D) It means the lawn is healthy.

B

3) Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?

A) The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.

B) The radio waves from the radio station have a wavelength of 97 million meters.

C) The "radio waves" received by your radio are not light waves like those we talk about in astronomy, but rather are a special type of sound wave.

D) The radio station broadcasts its signal with a power of 97 million watts.

A

4) Gamma rays have a very small

A) energy.

B) frequency.

C) mass.

D) wavelength.

D

6) Which of the following best describes why we say that light is an electromagnetic wave?

A) Light can be produced only by electric or magnetic appliances.

B) Light is produced only when massive fields of electric and magnetic energy collide with one another.

C) The passage of a light wave can cause electrically charged particles to move up and down.

D) The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

C

7) Which of the following statements about X rays and radio waves is not true?

A) X rays travel through space faster than radio waves.

B) X rays have shorter wavelengths than radio waves.

C) X rays and radio waves are both forms of light, or electromagnetic radiation.

D) X rays have higher frequency than radio waves.

A

9) Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?

A) It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.

B) The liquid molecules would quickly dissociate into a liquid of individual oxygen atoms. These atoms would then evaporate into a gas, and then become ionized to make a plasma.

C) It would sublimate into a gas, then the molecules would lose electrons until no electrons were left, then the molecules would dissociate into individual oxygen nuclei.

D) The cold temperature would first cause the oxygen to solidify. The solid would then sublimate into a gas, which would then become a plasma as the molecules lost their electrons, until finally it consisted of bonded pairs of oxygen nuclei stripped bare of any electrons.

A

11) Which of the following statements about electrons is not true?

A) Electrons orbit the nucleus rather like planets orbiting the Sun.

B) Within an atom, an electron can have only particular energies.

C) An electron has a negative electrical charge.

D) Electrons have very little mass compared to protons or neutrons.

E) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.

A

12) Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

A) The cloud is extremely hot.

B) The cloud is visible primarily because it reflects light from nearby stars.

C) The cloud is cool and very dense, so that you cannot see any objects that lie behind it.

D) The cloud is cool and lies between you and a hot star.

D

13) No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?

A) a hot, thin (low-density, nearly transparent) gas

B) a filament in a standard (incandescent) light bulb

C) a star

D) you

A

14) Which of the following statements about thermal radiation is always true?

A) A hot object emits more radiation per unit surface area than a cool object.

B) A cold object produces more total infrared and radio emission per unit surface area than a hot object.

C) A hot object produces more total infrared emission than a cooler object.

D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.

A

15) Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

A) It is much brighter than the Sun.

B) Its surface is cooler than the surface of the Sun.

C) It is much more massive than the Sun.

D) It is moving away from us.

B

16) The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?

A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.

B) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the blue light that is present in the Sun's spectrum.

C) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum.

D) There is no way to predict the answer to this question, since planets and stars are made of such different things.

A

17) All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?

A) The temperature of the corona's gas is some 1 to 2 million Kelvin.

B) The corona lies above the visible surface of the Sun.

C) The corona's gas consists mostly of hydrogen and helium.

D) The corona's structure is largely shaped by magnetic fields.

A

19) Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

A) Star X is moving away from us faster than Star Y.

B) Star Y is moving away from us faster than Star X.

C) Star X is hotter than Star Y.

D) Star X is moving away from us and Star Y is moving toward us.

A

20) If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

A) We must actually be observing moons orbiting the planet in opposite directions, not the planet itself.

B) The planet is rotating.

C) The planet is in the process of falling apart.

D) The planet is in the process of formation.

B

21) Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?

A) The total amount of light in the spectrum tells us the star's radius.

B) The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.

C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.

D) Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us.

A

22) Suppose that two stars are identical in every way—for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth—except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?

A) The faster rotating star has wider spectral lines than the slower rotating star.

B) The faster rotating star will have an emission line spectrum while the slower rotating star will have an absorption line spectrum.

C) The peak of thermal emission will be at a shorter wavelength for the faster rotating star than for the slower rotating star.

D) There is no way to tell the stars apart spectroscopically, because their spectra will be identical.

A