Astronomy Midterm 3 Exam - Questions and Answers (Complete Solutions)

Astronomy Midterm 3 Exam - Questions and Answers (Complete Solutions) 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 ...

Astronomy Midterm 3 Exam - Questions and Answers (Complete Solutions) 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 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. 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. 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. 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. 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. Which of the following cannot be described by a field? A) gravitational forces B) electrical forces C) magnetic forces D) radiation pressure 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 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. 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. 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 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 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. 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. 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. 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. 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 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 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. 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 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. 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. 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 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. 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. 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 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 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 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. 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.) 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. 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. When an atom loses an electron, it becomes A) sublimated. B) dissociated. C) ionized. D) an isotope. E) a plasma. 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 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. 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. 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. The study of energy levels in atoms is called A) special relativity. B) general relativity. C) quantum mechanics. D) classical mechanics. E) particle physics. 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. 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. 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. 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. 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. 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 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. 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. 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. 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. 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 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. 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 Dopple 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. 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.