ASTR 102 – TEST – MC05 & SA&TF – Flashcards
Unlock all answers in this set
Unlock answersquestion
1) If you have a 100-watt light bulb, how much energy does it use each minute? A) 6,000 joules B) 6,000 watts C) 600 joules D) 600 watts E) 100 joules
answer
A) 6,000 joules
question
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.
answer
B) absorbs most light.
question
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.
answer
A) angle of incidence = angle of reflection
question
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.
answer
C) transmits light well.
question
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.
answer
D) it reflects green light and absorbs other colors.
question
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.
answer
C) the filter transmits red light and absorbs other colors.
question
Which of the following cannot be described by a field? A) gravitational forces B) electrical forces C) magnetic forces D) radiation pressure
answer
D) radiation pressure
question
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
answer
E) all of the above
question
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.
answer
C) the distance between two adjacent peaks of the wave.
question
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.
answer
A) Longer wavelength means lower frequency and lower energy.
question
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
answer
B) radio, infrared, visible light, ultraviolet, X rays, gamma rays
question
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
answer
D) gamma rays, X rays, ultraviolet, visible light, infrared, radio
question
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.
answer
E) X rays travel through space faster than radio waves.
question
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.
answer
A) Neither X rays nor radio waves can penetrate the earth's atmosphere.
question
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.
answer
D) reflect visible light.
question
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.
answer
D) reflects visible light.
question
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
answer
C) millions
question
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
answer
C) a molecule containing two or more elements
question
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.
answer
E) a trillion times greater.
question
What is the name given to 2H? A) hydrogen B) helium C) deuterium D) tritium
answer
C) deuterium
question
How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have? A) a total charge of +17 B) a negative charge of -5 C) a positive charge of +7 D) a positive charge of +1 E) none of the above
answer
D) a positive charge of +1
question
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.
answer
D) A positive charge and a negative charge will attract each other.
question
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.
answer
A) Electrons orbit the nucleus rather like planets orbiting the Sun.
question
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
answer
D) several kilometers
question
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic weight? A) The atomic number is 79, and the atomic weight is 197. B) The atomic number is 79, and the atomic weight is 118. C) The atomic number is 118, and the atomic weight is 197. D) The atomic number is 118, and the atomic weight is 79.
answer
A) The atomic number is 79, and the atomic weight is 197.
question
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. If it is doubly ionized, what is the charge of the gold ion and how many electrons remain in the ion? A) The gold ion has a charge of +2 and 77 electrons. B) The gold ion has a charge of +2 and 79 electrons. C) The gold ion has a charge of -2 and 77 electrons. D) The gold ion has a charge of +2 and 2 electrons. E) The gold ion has a charge of +79 and no electrons.
answer
A) The gold ion has a charge of +2 and 77 electrons.
question
Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms isotopes of each other? A) Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons B) Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons C) Atom 1: nucleus with 92 protons and 143 neutrons, surrounded by 92 electrons Atom 2: nucleus with 92 protons and 146 neutrons, surrounded by 92 electrons D) Atom 1: nucleus with 1 proton and 0 neutrons, surrounded by 1 electron Atom 2: nucleus with 2 protons and 2 neutrons, surrounded by 2 electrons E) Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons
answer
C) Atom 1: nucleus with 92 protons and 143 neutrons, surrounded by 92 electrons Atom 2: nucleus with 92 protons and 146 neutrons, surrounded by 92 electrons
question
An atom of the element iron has an atomic number of 26 and an atomic weight of 56. If it is neutral, how many protons, neutrons, and electrons does it have? A) 26 protons, 30 neutrons, 26 electrons B) 26 protons, 30 neutrons, 30 electrons C) 26 protons, 56 neutrons, 26 electrons D) 13 protons, 43 neutrons, 13 electrons E) 13 protons, 56 neutrons, 13 electrons
answer
A) 26 protons, 30 neutrons, 26 electrons
question
Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion, and how many electrons will the ion have? A) It must be ionized three times; it now has five electrons. B) It must be ionized five times; it now has five electrons. C) It must be ionized five times; it now has three electrons. D) It doesn't have to be ionized; it just needs to gain five protons. E) It doesn't have to be ionized; it already has only three electrons.
answer
C) It must be ionized five times; it now has three electrons.
question
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.)
answer
B) a plasma consisting of positively charged ions and free electrons
question
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.
answer
C) molecules go from the solid phase to the gas phase.
question
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.
answer
A) the bonds between atoms in a molecule are broken.
question
When an atom loses an electron, it becomes A) sublimated. B) dissociated. C) ionized. D) an isotope. E) a plasma.
answer
C) ionized.
question
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
answer
E) electric potential energy
question
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.
answer
C) An electron moves from an upper energy level to a lower one.
question
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.
answer
C) ionized helium.
question
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.
answer
D) an amount of energy much smaller than a joule.
question
The study of energy levels in atoms is called A) special relativity. B) general relativity. C) quantum mechanics. D) classical mechanics. E) particle physics.
answer
C) quantum mechanics.
question
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.
answer
B) It releases a photon equal in energy to its own energy drop.
question
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.
answer
C) an emission line spectrum.
question
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.
answer
A) emits a photon of a specific frequency.
question
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.
answer
D) an absorption line spectrum.
question
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.
answer
D) have different sets of spectral lines.
question
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
answer
A) hot, thin gas
question
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.
answer
C) radiation that depends only on the emitting object's temperature.
question
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.
answer
D) a thermal emitter.
question
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.
answer
D) A hot object emits more total radiation per unit surface area than a cool object.
question
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.
answer
B) A hot object emits photons with a higher average energy than a cool object.
question
If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits A) 3 times more energy. B) 9 times more energy. C) 12 times more energy. D) 81 times more energy. E) none of the above
answer
D) 81 times more energy.
question
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.
answer
B) mostly X rays.
question
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.
answer
B) The total amount of light in the spectrum tells us the star's radius.
question
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.
answer
B) have wavelengths that are longer than normal.
question
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude? A) The star is moving toward us. B) The star is moving away from us. C) The star is getting hotter. D) The star is getting colder. E) The "star" actually is a planet.
answer
A) The star is moving toward us.
question
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude? A) The star is moving toward us. B) The star is moving away from us. C) The star is getting hotter. D) The star is getting colder. E) The "star" actually is a planet.
answer
B) The star is moving away from us.
question
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.
answer
B) A molecule has additional spectral lines due to changes in its rotational and vibrational energies.
question
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.
answer
A) The galaxy is moving away from you.
question
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.
answer
C) The one with the large redshift is moving away from us faster than the one with the small redshift.
question
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.
answer
D) The planet is rotating.
question
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.
answer
D) The blue star has a hotter surface temperature than the red star.
question
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.
answer
D) The line in the faster rotating star is broader.
question
What is the difference between energy and power? A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time. B) Power is measured in joules and energy is measured in watts. C) Power is used to describe energy of light, while the term energy has a broader meaning. D) There's no difference: Energy and power are different names for the same thing.
answer
A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
question
Visible light from a distant star can be spread into a spectrum by using a glass prism or ________. A) a diffraction grating B) adaptive optics C) a telescope D) a flat glass mirror
answer
A) a diffraction grating
question
Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond? A) They have a frequency of 4 hertz. B) They have a frequency of 2 hertz. C) We can calculate the wavelength of the ripples from their frequency. D) They have a wavelength of two cycles per second. x
answer
A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
question
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon? A) its temperature B) its acceleration C) its wavelength and energy D) the chemical composition of the object that emitted it
answer
C) its wavelength and energy
question
When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called ________. A) photons B) wavicles C) gamma rays D) frequencies
answer
A) photons
question
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation? A) gamma rays, X rays, ultraviolet, visible light, infrared, radio B) infrared, visible light, ultraviolet, X rays, gamma rays, radio C) radio, infrared, visible light, ultraviolet, X rays, gamma rays D) gamma rays, X rays, visible light, ultraviolet, infrared, radio
answer
A) gamma rays, X rays, ultraviolet, visible light, infrared, radio
question
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
answer
A) infrared and radio
question
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
answer
A) absorbs ultraviolet light
question
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
answer
C) several kilometers
question
Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)? A) They have different atomic mass numbers. B) They have different numbers of protons in their nucleus. C) hey have different numbers of electrons. D) They have different names.
answer
B) They have different numbers of protons in their nucleus.
question
Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number? A) atomic number = 6; atomic mass number = 13 B) atomic number = 6; atomic mass number = 7 C) atomic number = 13; atomic mass number = 6 D) atomic number = 7; atomic mass number = 13
answer
A) atomic number = 6; atomic mass number = 13
question
An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains ________. A) 4 electrons B) 6 electrons C) 10 electrons D) at least one electron
answer
A) 4 electrons
question
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
answer
C) molecules go directly from the solid phase to the gas phase
question
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.
answer
A) An electron begins in an excited state and then gains enough energy to jump to the ground state.
question
An atom that has fewer electrons than protons is called a/an ________. A) molecule B) solid C) ion D) plasma
answer
C) ion
question
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.
answer
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.
question
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
answer
A) radiation with a spectrum whose shape depends only on the temperature of the emitting object
question
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
answer
B) a shorter average wavelength
question
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.
answer
C) The wavelengths of spectral lines in the star's spectrum.
question
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.
answer
C) The wavelengths of spectral lines in the star's spectrum.
question
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
answer
A) have wavelengths that are longer than normal
question
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.
answer
A) The galaxy is moving away from you.
question
Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use? A) 6,000 joules B) 6,000 watts C) 100 watts D) 100 joules
answer
A) 6,000 joules
question
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.
answer
B) It absorbs red light and reflects green light.
question
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.
answer
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.
question
Gamma rays have a very small ________. A) energy B) frequency C) mass D) wavelength
answer
D) wavelength
question
Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength? A) 1 meter B) 1/300,000 meter C) 300 million meters D) A photon's wavelength cannot be determined from its frequency.
answer
A) 1 meter
question
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.
answer
C) The passage of a light wave can cause electrically charged particles to move up and down.
question
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.
answer
A) X rays travel through space faster than radio waves.
question
Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element? A) Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons; Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons. B) Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons. C) Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons; Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons. D) Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons; Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons. neutrons, surrounded by 7 electrons.
answer
B) Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7
question
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.
answer
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.
question
Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion? A) Charge = +2; number of remaining electrons = 8. B) Charge = -2; number of remaining electrons = 10. C) Charge = +2; number of remaining electrons = 6. D) Charge = +2; number of remaining electrons = 2.
answer
C) Charge = +2; number of remaining electrons = 6.
question
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.
answer
A) Electrons orbit the nucleus rather like planets orbiting the Sun.
question
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.
answer
D) The cloud is cool and lies between you and a hot star.
question
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
answer
A) a hot, thin (low-density, nearly transparent) gas
question
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.
answer
A) A hot object emits more radiation per unit surface area than a cool object.
question
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.
answer
B) Its surface is cooler than the surface of the Sun.
question
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.
answer
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.
question
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.
answer
A) The temperature of the corona's gas is some 1 to 2 million Kelvin.
question
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude? A) The star is moving away from us. B) The star is getting hotter. C) The star is moving toward us. D) The star is getting colder.
answer
C) The star is moving toward us.
question
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.
answer
A) Star X is moving away from us faster than Star Y.
question
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.
answer
B) The planet is rotating.
question
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.
answer
B) The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.
question
Suppose that two stars are identical in every wayfor example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earthexcept 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.
answer
A) The faster rotating star has wider spectral lines than the slower rotating star.
question
Energy and power are different words for the same thing.
answer
False
question
Process of Science: I am doing science when I already know the answer to my scientific question and I am searching for evidence in the natural world strictly to support what I know.
answer
False
question
Grass is green because it absorbs green light, reflecting all other colors.
answer
False
question
The shorter the wavelength of light, the higher its frequency.
answer
True
question
The greater the wavelength of light, the greater its energy.
answer
False
question
X rays, because they have more energy, travel through space faster than visible light.
answer
False
question
X rays are always more intense than radio waves.
answer
False
question
You are currently emitting electromagnetic waves.
answer
True
question
There are more atoms in a glass of water than stars in the observable universe.
answer
True
question
Atomic nuclei consist of protons and electrons.
answer
False
question
Electrons orbit an atomic nucleus like planets orbit the Sun.
answer
False
question
The atomic nuclei of the same element always have the same number of protons.
answer
True
question
The atomic nuclei of the same element always have the same number of neutrons.
answer
False
question
The energy levels for electrons vary from one element to another.
answer
True
question
The energy levels of an element and its ion are the same.
answer
False
question
Lines of a particular element appear at the same wavelength in both emission and absorption line spectra
answer
True
question
Any object moving relative to Earth will have a Doppler shift.
answer
False
question
Emission lines from different ionization states of the same element appear in the same place in the spectrum
answer
False
question
Atomic number refers to ________.
answer
the number of protons in an atom
question
Define atomic weight (or atomic mass).
answer
Atomic weight is the number of protons plus neutrons in an atom.
question
Suppose you have a chunk of water ice. Describe what happens to it, in terms of phases, as you raise the temperature to millions of degrees.
answer
The ice melts into liquid, then evaporates into gas. At higher temperatures, the water molecules dissociate atoms. At very high temperatures, the atoms are ionized.
question
An isotope of fluorine has 9 protons and 10 neutrons. What are the atomic number and atomic weight of this fluorine? If we added a proton to this fluorine nucleus, would the result still be fluorine? What if we added a neutron instead? Explain.
answer
The atomic number of fluorine is equal to the number of protons, 9. The atomic weight is equal to the number of protons plus neutrons, 19. If we added a proton, it would no longer be fluorine. If we added a neutron instead, it would just be another isotope of fluorine, with atomic number 9 but atomic weight 20.
question
The most common isotope of oxygen has atomic number 8 and atomic weight 16. Another isotope has two extra neutrons. What are the atomic number and atomic weight of this isotope?
answer
The atomic number would still be 8 because the number of protons wouldn't change, but the atomic weight would increase to 18.
question
The most common isotope of gold has atomic number 79 and atomic weight 197. How many protons and neutrons does the gold nucleus contain? Assuming the gold is electrically neutral, how many electrons does it have? If the gold is triply ionized, how many electrons does it have?
answer
The most common isotope of gold contains 79 protons and 118 neutrons. If it is neutral, it also contains 79 electrons. If the gold is triply ionized instead, it is missing 3 electrons and so has only 76 electrons.
question
The most common isotope of uranium is U-238, but the form used in nuclear bombs and nuclear power plants is U-235. Given that uranium has atomic number 92, how many neutrons are in each of these two isotopes?
answer
U-238 has 146 neutrons, and U-235 has 3 fewer, or 143 neutro
question
What do we mean when we say that electron energy levels in atoms are quantized?
answer
The electrons can have only specific energies and not amounts of energy in between.
question
Briefly explain why spectral lines are useful in determining the chemical composition of their source.
answer
Every chemical element has a unique set of atomic energy levels and therefore a unique set of spectral lines. Thus, by identifying spectral lines, we can identify the elements that produced them.
question
Briefly explain why spectral lines are useful in determining the temperature of their source.
answer
Different ionization states of the same element have different sets of spectral lines. Thus, we can identify the ionization state, which tells us about the temperature because higher temperatures are required to reach higher ionization states.
question
State the two laws of thermal radiation.
answer
1. Hotter objects emit more radiation per unit surface area. 2. Hotter objects emit photons with higher average energy.
question
Briefly explain how we can use spectral lines to determine an object's radial motion. Can we also learn the object's tangential motion (across our line of sight) from its spectral lines?
answer
By comparing the wavelength of the spectral lines in the object's spectrum to the rest wavelengths of the same lines, we measure the Doppler shift. This tells us the object's radial motion: A shift toward shorter wavelength means the object is moving toward us, and a shift to longer wavelength means it is moving away from us. We cannot learn anything about the object's tangential motion from its spectral lines because this does not affect the line positions.
question
The following questions refer to the diagram below. The levels represent energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. 1) Which transition represents an electron that absorbs a photon with 10.2 eV of energy? 2) Which transition represents the electron that emits a photon with the highest energy? 3) Which transition represents an electron that is breaking free of the atom? 4) Which transition, as shown, is not possible?
answer
1) B 2) A 3) E 4) D
question
Briefly explain why spectral lines are useful in determining the temperature of their source.
answer
Different ionization states of the same element have different sets of spectral lines. Thus, we can identify the ionization state, which tells us about the temperature because higher temperatures are required to reach higher ionization states.
question
State the two laws of thermal radiation.
answer
1. Hotter objects emit more radiation per unit surface area. 2. Hotter objects emit photons with higher average energy.
question
Suppose the surface temperature of the Sun were about 18,000 K, rather than 6,000 K. How much more thermal radiation would the Sun emit? How would the thermal radiation spectrum of the Sun be different?
answer
From the first rule of thermal radiation, we know that tripling the temperature of an object increases the amount of thermal radiation it emits per unit area by a factor of 34 = 81. Thus, increasing the surface temperature of the Sun from 6,000 K to 18,000 K would increase its thermal radiation by a factor of 81. The higher temperature of the Sun would shift the peak of its thermal radiation spectrum from its current place in the visible light region into the ultraviolet. The hotter Sun would emit more energy at all wavelengths, with the greatest output coming in the ultraviolet.
question
Briefly explain how we can use spectral lines to determine an object's radial motion. Can we also learn the object's tangential motion (across our line of sight) from its spectral lines?
answer
By comparing the wavelength of the spectral lines in the object's spectrum to the rest wavelengths of the same lines, we measure the Doppler shift. This tells us the object's radial motion: A shift toward shorter wavelength means the object is moving toward us, and a shift to longer wavelength means it is moving away from us. We cannot learn anything about the object's tangential motion from its spectral lines because this does not affect the line positions.
question
Briefly explain how we can use spectral lines to determine an object's rotation rate.
answer
Lines are wider for faster-rotating objects because parts of the object are rotating toward us and parts are rotating away from us.
