Ch. 5 - Concepts

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 toward us. B.) The star is getting hotter. C.) The star is moving away from us. D.) The star is getting colder.

A

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 X is moving away from us and Star Y is moving toward us. C.) Star Y is moving away from us faster than Star X. D.) Star X is hotter than Star Y. E.) Star X is coming toward us faster than Star Y.

A

Which of the following best describes why we say that light is an electromagnetic wave? A.) The passage of a light wave can cause electrically charged particles to move up and down. B.) Light can be produced only by electric or magnetic appliances. C.) Light is produced only when massive fields of electric and magnetic energy collide with one another. D.) The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

A

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 cool and lies between you and a hot star. B.) The cloud is cool and very dense, so that you cannot see any objects that lie behind it. C.) The cloud is visible primarily because it reflects light from nearby stars. D.) The cloud is extremely hot.

A

Which of the following statements about electrons is not true? A.) Electrons orbit the nucleus rather like planets orbiting the Sun. B.) An electron has a negative electrical charge. C.) Within an atom, an electron can have only particular energies. D.) 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. E.) Electrons have very little mass compared to protons or neutrons.

A

Which of the following statements about thermal radiation is always true? A.) All the light emitted by hot object has higher energy than the light emitted by a cooler object. B.) A hot object emits more radiation per unit surface area than a cool object. C.) A hot object produces more total infrared emission than a cooler object. D.) A cold object produces more total infrared and radio emission per unit surface area than a hot object.

A

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 more massive than the Sun. B.) Its surface is cooler than the surface of the Sun. C.) It is much brighter than the Sun. D.) It is moving away from us.

B

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 star B.) a hot, thin (low-density, nearly transparent) gas C.) you D.) a filament in a standard (incandescent) light bulb

B

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.) 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. B.) 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. 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.

B

Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use? A.) 100 joules. B.) 6,000 joules C.) 6,000 watts D.) 100 watts

B

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 blue 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 red light that is present in the Sun's spectrum. C.) There is no way to predict the answer to this question, since planets and stars are made of such different things. D.) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum.

B

Which of the following statements is true of green grass? A.) It means the lawn is healthy. B.) It absorbs red light and reflects green light. C.) It transmits all colors of light except green. D.) It absorbs red light and emits green light.

B

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 4 protons and 5 neutrons, surrounded by 4 electrons; Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons B.) 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 C.) 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 D.) 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

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 corona's structure is largely shaped by magnetic fields. B.) The corona lies above the visible surface of the Sun. C.) The corona's gas consists mostly of hydrogen and helium. D.) The temperature of the corona's gas is some 1 to 2 million Kelvin.

D

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 = 2. C.) Charge = -2; number of remaining electrons = 10. D.) Charge = +2; number of remaining electrons = 6.

D

Gamma rays have a very small ______. A.) mass B.) frequency C.) energy D.) wavelength

D

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

D

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 peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths. B.) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals. C.) 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. D.) The total amount of light in the spectrum tells us the star's radius.

D

Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength? A.) A photon's wavelength cannot be determined from its frequency B.) 300 million meters C.) 1/300,000 meter. D.) 1 meter

D

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 peak of thermal emission will be at a shorter wavelength for the faster rotating star than for 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.) There is no way to tell the stars apart spectroscopically, because their spectra will be identical. D.) The faster rotating star has wider spectral lines than the slower rotating star.

D

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 have a wavelength of 97 million meters. B.) 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. C.) The radio station broadcasts its signal with a power of 97 million watts. D.) 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.

D

Which of the following statements about X rays and radio waves is not true? A.) X rays and radio waves are both forms of light, or electromagnetic radiation. B.) X rays have higher frequency than radio waves. C.) X rays have shorter wavelengths than radio waves. D.) X rays travel through space faster than radio waves.

D