FinalAstronomy 102Fall 20051. The exam should take ∼2 hours to complete.2. There are 100 multiple choice questions.3. Choose the one alternative that best completes the statement or answers the question.4. If you leave the classroom during the exam, you cannot return!5. When you are done, please turn in this copy of the test and leave the room quietly!6. If you have a question, please raise your hand.7. Have a great vacation!!!!Astronomy 102 Final Fall 20051. Choose the best arrangement of the following items according to size, from the smallestto the largest.A. atom, planet, Sun, galaxy, cluster of galaxies.B. proton, galaxy, open cluster, cluster of galaxies.C. proton, star, galaxy, Solar System.D. Sun, Solar System, cluster of galaxies, globular star cluster.2. Which of the following is the most massive?A. The Sun.B. The brightest main sequence star in the Large Magellanic Cloud.C. The planet Jupiter.D. The neutron star at the center of the Crab Nebula.E. The white dwarf Sirius B.3. Suppose you were standing on a planet that had the same mass as the Earth, but whoseradius was three times larger. Compared to the surface of the Earth, the gravitationalforce you would feel on the surface of the planet would:A. be the same, because the masses of both planets are identical.B. be 3 times weaker.C. be 3 times stronger.D. be 9 times weaker.E. be 6 times weaker.4. Suppose there were some remarkable breakdown in physics and the radius of the Suninstantly shrank to less than its Schwarzschild radius, without changing its mass. Whichof the following would be true?A. The Sun would become a black hole, because its radius was smaller than theSchwarzschild radius.B. The radius of the Earth’s orbit would shrink, because gravity depends onradius.C. The radius of the Earth’s orbit would expand, because the Earth was nowfarther away from most of the Sun’s mass.D. The Sun would still be a main sequence star, since it was still 1 solar mass.E. The temperature of the Sun would be cooler, since it was now denser.Page 1 of 205. Why does a ball speed up when you drop it?A. The gravitational force increases when the ball moves closer to the Earth.B. Energy is conserved, and as the ball loses gravitational potential energy it mustgain kinetic energy.C. Angular momentum is conserved, so the ball must speed up as it moves closerto the Earth.D. The ball doesn’t speed up, but moves at constant velocity because all forcescancel.E. It is eager to reach the ground.6. Another name for an isolated proton might be aA. hydrogen ion.B. hydrogen isotope.C. helium ion.D. neutron.7. If you could add a proton to an atom to create a new stable, isolated atom, you wouldhave createdA. a different element with a positive charge.B. an isotope of the original element.C. a fission reaction.D. a neutron and a positron.8. A cubic centimeter of lead has a greaterthan a cubic centimeter of styrofoam.A. massB. mass densityC. number densityD. volumeE. more than one of the above9. As you increase the temperature of a gasA. the average speed of the particles in the gas increases.B. the fraction of the particles that are neutral (i.e. un-ionized) increases.C. the total energy of the gas increases.D. more than one of the above.E. none of the abovePage 2 of 2010. If you were going to design a pair of glasses for seeing animals at night, you would wantthem to convertA. infrared photons to X-ray photons.B. X-ray photons to optical photons.C. infrared photons to optical photons.D. optical photons to UV photons.11. True or False? Everything in the Universe emits thermal radiaion.A. True. B. False.12. My can of root beer is hotter than Peter’s can of cola beverage (which he sensibly storedin the refridgerator). Considering only the thermal radiation they emit, which of thefollowing is true.A. My root beer emits more infrared photons (per unit area) than Peter’s cola.B. My root beer emits a larger fraction of ultraviolet photons than Peter’s cola.C. My root beer emits more ultraviolet photons (per unit area) than Peter’s cola.D. All of the above.E. more than one of the above.13. Suppose that light with wavelengths shorter than 90 nm can ionize a particular atom.Suppose that a photon with a wavelength of 30 nm hits the atom. What happens?A. The electron will get excited and then release a photon with a wavelength of30 nm when it goes back to the ground state.B. The electron will be ionized and will escape the atom.C. Nothing.D. Can’t decide without additional information.E. None of the above.14. Suppose that light with wavelengths shorter than 90 nm can ionize a particular atom.Suppose that a photon with a wavelength of 300 nm hits the atom. What happens?A. The electron will get excited and then release a photon with a wavelength of300 nm when it goes back to the ground state.B. The electron will be ionized and will escape the atom.C. Nothing.D. Can’t decide without additional information.E. None of the above.Page 3 of 2015. If two intrinsically identical stars are at different distances from the Earth, the moredistant star will have aA. bluer color.B. higher luminosity.C. lower luminosity.D. lower apparent flux.16. Four stars are all members of the same star cluster. Their absolute magnitudes are 10,7, -1, -10. Which star appears brightest from the Earth?A. the first.B. the second.C. the third.D. the fourth.17. Suppose you have measured a parallax distance of 2 parsecs to a nearby main sequenceM-star. Suppose you observe another main sequence M-star that is 4 times fainter. Thedistance to the second star isA. 4 parsecs.B. 6 parsecs.C. 8 parsecs.D. 16 parsecs.E. 32 parsecs.18. Why does fusion of Hydrogen release energy?A. Fusion breaks the electromagnetic bonds between hydrogen atoms, releasingenergetic photons.B. The mass of a helium nucleus is smaller than the mass of four protons.C. The mass of a helium nucleus is larger than the mass of four protons.D. The velocity of four protons is larger than the velocity of a helium nucleus.19. Suppose that the strength of the charge on the proton were increased. To maintain itssame luminosity, the radius of a of main sequence star would have toA. increase.B. decrease.C. not change.Page 4 of 2020. If the rate of hydrogen fusion within the Sun were to increase, the temperature of thecore would increase, causing the core of the Sun to subsequentlyA. contract and decrease in temperature.B. expand and increase in temperature.C. expand and decrease in temperature.D. stay the same size
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