Astronomy 100 — Exam 1

Prof. WangExam Version c

INSTRUCTIONS: Please write only your name and ID number on BOTH this sheet and the computer grading form.Use a #2 Pencil on the computer grading form. Be careful to match up your question number with the number on the

computer form, and thoroughly erase all changed answers and stray marks on the form.Be sure you have all 58 questions in the exam!

OPTIONAL “PYRAMID” GRADING: You may take this exam sheet and an extra computer grading form homewith you, rework the problems, and bring them back to turn in during the next class period. If you choose thisoption, the in-class version will count for 75% of your exam grade, and the take-home version will count for 25% ofyour exam grade. If you do not choose this option, the in-class version will count for 100%.

Make sure to circle each multiple choice answer on this sheet you think is right, so when you get home you’ll know howyou answered in class.

Reference Section

M� = MSun = 2× 1030 kg M⊕ = MEarth = 6× 1024 kg 1◦ = 60 arcminutes1 mm = 10−3 m 1 km = 103 m 1 kg = 2.2 pounds on Earth’s surface

1nm = 10−9 m 1µm = 10−6 m 1 AU = 1.5× 1011 m 1 ly = 9.5× 1015 mc = 3.0× 108 m s−1 G = 6.7× 10−11 m3 kg−1 s−2

P 2yr = a3

AUF = ma F =

GMm

d2

λν = c E = hν λpeak(mm) = 2.93/T (K)

L = 4πσT 4R2 L = f × 4πd2

MULTIPLE CHOICE QUESTIONS: Identify the choice that best complete the statement or answers the question.

1. BE SURE TO ANSWER THIS QUESTION This test is VERSION C. What version of the test do you have?A. VERSION c. B. wrong! C. wrong! D. wrong! E. wrong!

2. 2.9 x 107 is the same asA. 2.9 thousand B. 29 thousand C. 290 thousand D. 2.9 million E. 29 million

3. The angular sizes of the Moon and Sun as seen from Earth are both about 0.5 degrees. The Sun is about 400 timesfarther away than the Moon. From this we can conclude that the Moon’s diameter is ——- the Sun’s diameter.

A. nearly the same as C. about 2 times smaller than E. about 400 times smaller thanB. about 2 times larger than D. about 400 times larger than

4. A ”light-year” can be defined asA. the distance that light travels during the time that Earth revolves around Sun once.B. the distance between Sun and the nearest star.C. the distance that Earth travels in one year as it orbits Sun once.D. the time required for light to travel between Earth and Sun.E. the time required for light to travel between Sun and the nearest star.

5. When does the new moon set?A. at sunset B. at noon. C. it never rises. D. at midnight. E. at sunrise.

6. Why does the scientific community prefer to use the metric system over the system (e.g., feet and miles) we normallyuse in our everyday lives?

A. The metric system is more accurate.B. The metric system can deal with larger numbers than the other system, and astronomy always deals with

large numbers.C. The metric system allows for much easier calculations.D. None of the above. The scientific community does not prefer to use the metric system because everything in

science is based upon inches, feet and miles.E. Other countries have always used metric system.

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7. If the Sun were a grapefruit in this room, the nearest star (Proxima Centauri) would beA. more-or-less another grapefruit on the West Coast.B. a poppyseed about 15 m away.C. a peppercorn about 100 m away.D. more-or-less another grapefruit on the other side of campus.E. a creampuff at Bart’s.

8. The difference between radiation and sound is thatA. radiation has wavelength and frequency, whereas sound does not.B. sound needs a physical medium through which to travel, whereas radiation does not.C. radiation travels much slower than sound.D. radiation travels at different speed, depending on wavelength, whereas sound always travels at the same

speed.E. radiation can show Doppler effects, whereas sound cannot.

9. The principle use of dividing the sky up into constellations today is toA. identify regions and/or designate positions for objects in the sky.B. allow historians to recall and/or identify the ancient gods and goddesses.C. establish the basis for the retelling of mythological stories of the stars.D. allow astrologers to predict the future.E. prohibit stars from crossing the borders.

10. For mapping purposes, the Earth is divided into two equal halves by an imaginary line called the equator. Likewise,the sky is divided into two equal halves by an imaginary line called the

A. celestial equator. B. ecliptic. C. line of nodes. D. zodiac.E. none of the above. Neither are divided equally.

11. Absolute zero isA. zero degrees Celsius.B. the temperature at which water freezes.C. the temperature at which atoms have no remaining energy from which we can extract heat.D. both a and bE. none of the above

12. In the hydrogen atom, the electron and proton are bound together byA. gravitational force. C. electromagnetic force. E. none of the above.B. nuclear force. D. chemical force.

13. Each day, from a point on Earth just south of the equator, most stars appear toA. remain stationary overhead. D. rise in the east and set in the west.B. move to the north. E. rise in the west and set in the east.C. move to the south.

14. A hydrogen atom making a direct transition from an upper energy level to the ground (lowest) energy levelA. emits a photon which has an energy which depends on the temperature of the atom.B. emits a photon with an energy exactly equal to the difference in energy between the two states.C. experiences a Doppler shift.D. absorbs a photon which has an energy which depends on the temperature of the atom.E. emits a continuous spectrum.

15. Blackbody radiation isA. due to the thermal motion of electrons, which emit photonsB. continuous (lineless) in its energy spectrumC. invisible to the naked eyeD. confined to a few specific wavelengths, depending on the materialE. a and b

16. Which of the following statements about radiation is TRUE?A. Ice cubes at a temperature below the freezing point do not emit black body radiation.B. Solid objects emit radiation. Objects composed of gases do not.C. The maximum intensity of radiation emitted by a human body is at infrared wavelengths.D. Hot objects emit less short wavelength radiation than do cooler objects.E. Hot objects emit less amount of radiation than do cooler objects.

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17. If the Earth suddenly reveresed its direction of spin, without changing its orbital direction around the Sun,A. the Sun would rise in the West and set in the East.B. the stars would move across the sky counterclockwise around Polaris.C. over the year the Sun would travel in reverse through the signs of the Zodiac compared to now.D. summer would come six months later.E. All of the Above.

18. What causes seasons here on planet Earth?A. The tilt of the Earth’s axis.B. periodic changes in the heat retention of the Earth’s atmosphere.C. The elliptical orbit of the Moon.D. because of the alignment of the solar and lunar cycles.E. the Earth’s elliptical orbit brings it closer and farther from the Sun.

19. Newton concluded that some force had to act on the Moon becauseA. a force is needed to keep the Moon in motion.B. a force is needed to pull the Moon outward.C. the Moon moved at a constant velocity.D. a force is needed to pull the Moon away from straight-line motion.E. all of the above

20. From smallest to largest, what is the correct order of the following distances? (ly stands for light year)A. 1 cm, 1 km, 1 ly, 1 AU C. 1 km, 1 AU, 1 cm, 1 ly E. 1 km, 1 cm, 1 ly, 1 AUB. 1 AU, 1 ly, 1 cm, 1 km D. 1 cm, 1 km, 1 AU, 1 ly

21. All planetary orbits areA. circles with the Sun at the center. D. circles with the Sun at one focus.B. ellipses with the Sun at the center. E. ellipses with the Sun at one focus.C. ovals with the Sun at the center.

22. The sun isA. a star D. all of the aboveB. 1 AU from Earth. E. none of the above.C. more than 100 times the diameter of Earth.

23. A red ball is red becauseA. it only emits frequencies corresponding to redB. it only reflects frequencies corresponding to redC. it only transmits frequencies corresponding to redD. it only absorbs frequencies corresponding to redE. none of the above.

24. What phase would the Earth appear to be in if you were standing on the Moon at Full Moon?A. New C. Crescent E. Only the Moon can show phasesB. Waxing gibbous D. Full

25. From smallest to largest, the correct order of the following objects isA. Earth’s orbit, Jupiter, Milky Way Galaxy, Solar SystemB. Jupiter, Earth’s orbit, Solar System, Milky Way GalaxyC. Earth’s orbit, Milky Way Galaxy, Solar System, JupiterD. Solar System, Earth’s orbit, Milky Way Galaxy, JupiterE. Milky Way Galaxy, Jupiter, Earth’s orbit, Solar System

26. The principle difference between radio waves and visible light isA. radio waves travel at the speed of sound.B. radio waves carry substantially more energy per photon.C. only visible light can travel through the vacuum of space.D. blackbodies cannot produce radio waves.E. radio waves have a longer wavelength than visible light.

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27. An astronaut has a mass of 60 kilograms before she takes off in her ship. When she reaches Earth orbit, her massis ——, when she lands on the Moon, her mass is ——.

A. zero; smaller than on EarthB. much smaller than on Earth, smaller than on EarthC. zero; the same as on EarthD. the same as on Earth; the same as on EarthE. much smaller than on Earch, zero

28. The circular shape of the Earth’s shadow on the Moon led early astronomers to conclude thatA. the Earth is a sphere. D. the Moon must orbit the Sun.B. the Earth is at the center of the Solar system. E. the Moon is a sphere.C. the Earth must be at rest.

29. If light takes 8 minutes to reach the earth from the sun and 5 hours to reach Pluto, what is the distance from thesun to Pluto?

A. 5 AU B. 37.5 AU C. 37.5 ly D. 5 ly E. 0.6 ly

30. The sun is on the celestial equator at the times ofA. the vernal equinox and the summer solstice.B. the autumnal equinox and the vernal equinox.C. the summer solstice and the winter solstice.D. the autumnal equinox and the winter solstice.E. the sun is on the ecliptic and is never on the celestial equator.

31. If the Moon were two times closer to the Earth, the gravitational force between them would be .A. 0 B. 1/4 as strong C. half as strong D. twice as strong E. 4 times as strong

32. The of a gas is a measure of the average speed of the particles in the gas.A. heat B. composition C. temperature D. blue shift E. binding energy

33. Which of the following radiation has wavelengths that are longer than visible light?A. Gamma-rays C. Infrared radiation E. a, b and d aboveB. Ultraviolet light D. X-rays

34. As a black body is cooled the wavelength of maximum intensity willA. decrease. D. stay the same, but the frequency will decrease.B. increase. E. none of the above are true.C. stay the same, but the frequency will increase.

35. The terms speed and velocity are popularly used interchangeably, but Newton made an important distinction. Howdoes speed differ from velocity?

A. Speed is in miles per hour, while velocity is in kilometers per hour.B. Speed involves a direction of motion, while velocity involves only the size of the change in position per unit

time.C. Velocity adds a directional component to the speed.D. a and b above.E. Velocity describes the acceleration of an object, whereas speed does not.

36. An atom can be excitedA. if it emits a photon. D. a and b aboveB. if it collides with another atom or electron. E. b and c aboveC. if it absorbs a photon.

37. If the Earth were tipped 35◦ instead of 23.5◦, seasons on Earth would beA. hotter in the northern hemisphere, colder in the southernB. much shorterC. much less severeD. much more severeE. b and d

38. You can view a total lunar eclipse if the Moon is inA. the Moon’s penumbra C. the Earth’s penumbra E. the Earth’s umbraB. the Moon’s umbra D. the Earth’s umbrella

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39. The Sun appears in front of a different constellation each month due to theA. the Earth’s rotation on its axis.B. the Earth’s orbital motion around the Sun.C. the Sun’s motion around the center of the Milky Way Galaxy.D. precession of the rotation axis of the Earth.E. Moon’s orbit around the Earth.

40. High (spring) tide during the New Moon occurs atA. Midnight C. Midnight and Noon E. 6 am and 6 pmB. 6 pm D. Noon

41. The Copernican model of the universe was important because itA. was a heliocentric model.B. contained epicycles.C. included elliptical orbits.D. made very accurate predictions for the positions of the planets.E. all of the above

42. As Moon revolves around Earth once, it rotatesA. once. B. about 29 times. C. 24 times. D. 365 times.E. none of the above. Moon does not rotate.

43. Each day, the Moon rises aboutA. the same time. C. It depends on the year E. It depends on the season.B. an hour later. D. an hour earlier.

44. Ocean tides are caused primarily byA. seismic pressure waves beneath the surface. D. sunlight reflecting off waves.B. the Moon’s gravitational pull. E. All of the above.C. tectonic motion of the spreading ocean floor.

45. If an atom absorbs a photon,A. other photons summing to the same total energy may later be emitted.B. the photon must have the right energy for the atom’s energy levels.C. the atom will gain energy.D. the atom will move into a higher energy level.E. All of the above.

46. A beam of light from a laser has a wavelength of 600 nm, what is the frequency of this light?A. 5 x 1014 Hz B. 6000 Hz C. 3 x 108 m/s D. 2 x 10−15 Hz E. 1.8 x 1012 Hz

47. A lunar eclipse could never occurA. at high tide. D. within a couple of weeks of a solar eclipse.B. at Spring tide. E. at Harvest Moon.C. at Neap tide.

48. According to Kepler’s laws, a planet moves fastest in its orbit whenA. it is closest to Earth. D. it first rises at night.B. it is closest to the Sun. E. the nights are shortest.C. it is undergoing a retrograde loop.

49. An object moving around in a perfect circle at a constant speedA. is experiencing a force. C. also has a constant velocity. E. All of the AboveB. is not accelerating. D. must also be rotating.

50. Which of the following properties causes an object to experience a gravitational force?A. being in a magnetic fieldB. undergoing rotationC. experiencing pressure from an atmosphere (or other gases)D. having massE. All of the Above

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51. A rocket blasts propellant out of its thrusters and ”lifts off,” heading into space. What provided the force to liftthe rocket?

A. The propellant pushing against air molecules in the atmosphere.B. The propellant heating and expanding the air beneath the rocket, and so pushing the rocket upC. The action of the propellant accelerating down, giving a reaction force to the rocketD. The propellant reversing direction as it strikes the ground below the rocket, then bouncing back and pushing

the rocket upE. The propellant producing a vacum in front the rocket

52. If you apply the same force to two carts, the first with a mass of 100 kg, the second 50 kg, the acceleration of the100 kg cart will be —— the acceleration of the 50 kg cart.

A. the same as C. 2 times smaller than E. 50 times smaller thanB. 2 times larger than D. 50 times larger than

53. A spring tide occurs wheneverA. the Earth is closest to the Sun in its orbit.B. the Moon is in the springtime constellations of the Zodiac.C. the Moon is full or new.D. the Sun crosses the celestial equator.E. Only when all of the above conditions are met.

54. If the net force on an object doubles, then its —– also doubles.A. acceleration B. speed C. mass D. velocity E. All of the Above

55. An object emitting a ”black body” spectrum emits over a broad range of wavelengths, but with a peak whichdepends on its

A. absorption lines. C. mass. E. temperature.B. color. D. radius.

56. When a photon interacts with an atom, what changes occur in the atom?A. The photon becomes trapped in orbit. D. The mass of the nucleus increases.B. An electron changes its orbital. E. The nucleus begins to glow.C. The atomic number increases.

57. Object A has a temperature of 200 degrees Kelvin, whereas object B has that of 600 degrees.A. Object B emits 3 times more radiation than object A.B. Object B emits 9 times more radiation than object A.C. Object B emits 27 times more radiation than object A.D. Object B emits 81 times more radiation than object A.E. Object B emits the same amount of radiation as object A.

58. Several times on Star Trek, Mr. Spock fired his phaser at a rock to heat it when he was trapped on a cold planet.Suppose Mr. Spock increased the temperature of a rock to 3 times its initial value. The rock’s blackbody luminositywould increase...

A. 3 times B. 6 times C. 9 times D. 27 times E. 81 times

Please answer the following survey questions:

59. This test was I expected.A. much harder than C. about as hard as E. a lot easier thanB. a little harder than D. a little easier than

60. The course has been I expected based on my impression after attending the first week.A. much harder than C. as difficult as E. much easier thanB. harder than D. easier than

61. I would get more out of this course if the level were it has been so far.A. much harder than C. about the same as E. much easier thanB. harder than D. easier than

Write two things you don’t particularly like about the class. Rate each on a scale of 1-5 with 1=”I don’t care for this”and 5=”this really bites”.

Finally, please comment on what Prof. Wang may do to help you gain a better experience from the class.

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Key for exam1c1. A2. E3. E4. A5. A

6. C7. A8. B9. A

10. A

11. C12. C13. D14. B15. E

16. C17. A18. A19. D20. D

21. E22. D23. B24. A25. B

26. E27. D28. A29. B30. B

31. E32. C33. C34. B35. C

36. E37. D38. E39. B40. C

41. A42. A43. B44. B45. E

46. A47. C48. B49. A50. D

51. C52. C53. C

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54. A55. E

56. B57. D58. E