Astronomy 100
Mid–Term Exam N.1
Section 3 (79331), Fall 2014
Prof. Mauro Giavalisco
Exam Version A
INSTRUCTIONS: Make sure that you write your name and ID number on the SCANTRON sheet that you hand
in. You may keep the exam pages for your reference.
Be sure you have all 6 pages of the exam!
Read each question very carefully. Don’t rush your answer. Choose the letter of the response that you think best answers
the question.
MULTIPLE CHOICE QUESTIONS: If there are any questions you cannot answer because you find them too
ambiguous or too poorly worded to allow you to make a definite choice, explain your difficulty in the space at the
end of the exam, and you may get credit for those questions. You must be able to demonstrate that you understand
the material to receive credit.
Reference Section
M⊙ = MSun = 2 × 1030 kg
M⊕ = MEarth = 6 × 1024 kg
1◦ = 60 arcminutes
1 mm = 10−3 m
1 km = 103 m
1 kg = 2.2 pounds on Earth’s surface
−9
1nm = 10 m
1µm = 10−6 m
1 AU = 1.5 × 1011 m
1 ly = 9.5 × 1015 m
Radius of Earth = 6378 km
Radius of Moon = 1700 km
Distance to Moon = 380, 000 km
c = 3.0 × 108 m s−1
G = 6.7 × 10−11 m3 kg−1 s−2
GM m
2
Pyr
= a3AU
F = ma
F =
R2
∆λ
λ − λlab
v
λν = c
E = hν
h = 6.626×10−34 Joule sec
λpeak (mm) = 2.93/T (K)
=
=
λlab
λlab
c
1. The principal difference between radio waves and visible light is
A. radio waves travel at the speed of sound.
B. radio waves carry substantially more energy per photon.
C. radio waves have longer wavelength than visible light.
D. only visible light can travel through the vacuum of space.
E. blackbodies cannot produce radio waves.
2. A friend of yours tells you that they saw the constellation Orion high in the sky at 4 a.m. this morning. You are
not particularly interested in getting out of bed so early. How many months will you have to wait until you can see
Orion in the same place in the sky at midnight?
A. one month
B. two months
C. three months
D. four months
E. ten months
3. Electromagnetic radiation is
A. energy associated with a traveling wave of magnetic and electric fields
B. heat
C. confined to a few specific wavelengths, depending on the material
D. invisible to the naked eye
E. a and b
4. What phase would the Earth appear to be in if you were standing on the Moon at New Moon?
A. Waxing gibbous
C. New
E. Only the Moon can show phases
B. Crescent
D. Full
5. The phenomenon that causes the position of the Earth’s celestial poles to move among the stars is called
A. precession
C. retrograde motion
E. continental drift
B. parallax
D. regression
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6. You see two equally bright stars in the night sky. One clearly looks red, and the other appears blue. Which of the
two is emitting more energy?
A. the color does not provide enough information to answer the question.
B. the brighter star.
C. the red star.
D. the blue star.
E. they are the same.
7. The Copernican model of the universe was important because it
A. contained epicycles.
B. included elliptical orbits.
C. made very accurate predictions for the positions of the planets.
D. was a heliocentric model.
E. all of the above
8. Gravity
A. is the attraction between all objects with mass.
B. is the result of the pressure of the atmosphere on us.
C. occurs between objects that are touching each other (or that are both touching the atmosphere).
D. is the force larger objects exert on smaller ones.
E. is caused only by planets and the Sun.
9. If the Sun were a grapefruit in this room, the nearest star (Proxima Centauri) would be
A. a poppyseed about 15 m away.
D. another grapefruit on the West Coast.
B. a peppercorn about 100 m away.
E. a creampuff at Bart’s.
C. another grapefruit on the other side of campus.
10. The primary reason for deploying telescopes in space (space telescopes) is because
A. they avoid the blurring by the Earth’s atmosphere
B. the can observe e.m. wavelengths that would otherwise be blocked by the atmosphere
C. a and b
D. the sky is darker
E. we can look for alien life
11. When light passes through matter, the following generally happens
A. light is blocked by matter
C. nothing happens
B. light is absorbed by matter
D. light becomes redder
E. light becomes bluer
12. Low tide during the New Moon occurs at
A. Midnight
C. 6 pm
B. 6 am and 6 pm
D. Midnight and Noon
E. Noon
13. The speed of light
A. depends on its color
B. slows down when it is stretched by the curved space–time
C. is equal to 3.0 × 108 km/hour
D. a and c
E. is always the same regardless of the relative motion of the observer and the light source
14. What is the smallest diameter a coin has to have so that when held at arm’s length it can totally block the Sun?
(assume an arm’s length is equal to 1 meter).
A. 2 mm
B. 1 foot
C. 0.5 nm
D. ≈1 cm
E. 1 inch
15. If the Moon were two times closer to the Earth, the gravitational force between them would be
A. 1/4 as strong
C. twice as strong
E. 0
B. half as strong
D. 4 times as strong
.
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16. The Sun appears in front of a different constellation each month due to the
A. the Sun’s motion around the center of the Milky Way Galaxy.
B. precession of the rotation axis of the Earth.
C. Moon’s orbit around the Earth.
D. the Earth’s rotation on its axis.
E. the Earth’s orbital motion around the Sun.
17. From smallest to largest, the correct order of the following objects is
A. Earth’s orbit, Jupiter, Milky Way Galaxy, Solar System
B. Earth’s orbit, Milky Way Galaxy, Solar System, Jupiter
C. Solar System, Earth’s orbit, Milky Way Galaxy, Jupiter
D. Milky Way Galaxy, Jupiter, Earth’s orbit, Solar System
E. Jupiter, Earth’s orbit, Solar System, Milky Way Galaxy
18. Newton concluded that some force had to act on the Moon because
A. a force is needed to keep the Moon in motion.
B. a force is needed to pull the Moon away from straight-line motion.
C. a force is needed to pull the Moon outward.
D. the Moon moved at a constant velocity.
E. all of the above
19. Electromagnetic radiation can be
A. reflected, transmitted, absorbed and emitted.
B. accelerated
C. only deflected
D. slowed down to a halt
E. All of the above
20. The group of constellations through which the Sun passes as it moves along the ecliptic is called the
A. zodiac
B. deferent
C. celestial equator D. equinox
E. retrograde loop
21. In which situation would tides be the strongest?
A. the Moon, Sun and all planets are all aligned alone the same direction.
B. the Moon’s and the Sun are at 90 degrees
C. the Moon and the Sun are opposite to each other respect to Earth.
D. tides always have the same intensity.
E. all of the above.
22. If a external force F is applied on a moving object along the direction of motion, the total momentum of that
object
A. remains the same because total momentum is conserved.
B. changes by an amount proportional to 1/F 2 .
C. changes by an amount proportional to F .
D. the strength of the momentum remains the same, but its direction changes.
E. Both C and D.
23. Each day, from a point on Earth south of the equator, most stars appear to
A. remain stationary overhead.
D. move to the north.
B. rise in the east and set in the west.
E. move to the south.
C. rise in the west and set in the east.
24. Kepler’s second law (“law of equal areas”) expresses the fact that
A. the Sun is at one focus.
D. bigger planets have more area.
B. distant planets have more area.
E. All of the above.
C. planets move faster near to the Sun.
25. All planetary orbits are
A. circles with the Sun at the center.
B. ellipses with the Sun at the center.
C. ellipses with the Sun at one focus.
D. ovals with the Sun at the center.
E. circles with the Sun at one focus.
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26. A lunar eclipse can only occur when the Moon is
A. Full.
B. New.
C. Waxing.
27. The third quarter moon rises
A. at about noon.
B. at about midnight.
E. during the second week of each calendar month.
D. Waning.
C. at sunset.
E. Blue.
D. at sunrise.
28. You can view a total lunar eclipse if the Moon is in
A. the Moon’s penumbra
C. the Earth’s penumbra
B. the Moon’s umbra
D. the Earth’s umbra
E. the Earth’s umbrella
29. Each day, the Moon rises about
A. the same time.
B. It depends on the year
E. It depends on the season.
C. an hour later.
D. an hour earlier.
30. 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 cm, 1 km, 1 AU, 1 ly
E. 1 AU, 1 ly, 1 cm, 1 km
B. 1 km, 1 AU, 1 cm, 1 ly
D. 1 km, 1 cm, 1 ly, 1 AU
31. A mile is bigger than a kilometer. Let’s assume that the mile is used as the unit of length and the second as the
unit of time. Compared to using the kilometer as the unit of length, the number that expresses the measure of any
given velocity in miles/ per hour is
A. larger
B. smaller
C. the same
D. it depends on the conversion factor
E. it depends on the speed and the adopted unit of time
32. Due to tides raised on the Earth by the Moon, the Moon is gradually moving FURTHER from the Earth. The
average distance between the Earth and Sun remains constant. How will solar eclipses be different in the distant
future as a result of the increasing distance of the Moon from the Earth?
A. Total solar eclipses will occur only at Full Moon.
B. Total solar eclipses will last considerably longer.
C. Total solar eclipses will no longer occur.
D. Total solar eclipses will be visible only for the Earth’s Southern Hemisphere.
E. Total solar eclipses will occur at every New Moon.
33. How many arcseconds are there in one arcminute?
A. 1
B. 24
C. 60
D. 360
E. 3600
34. Which physical law describing gravitational motions can explain the fact that comets spend most of their time far
away from the Sun and little time close to the Sun?
A. Newton’s Third Law.
D. The Law of Universal Gravitation.
B. Galileo’s Law of Inertia.
E. Kepler’s Third Law.
C. Kepler’s Second Law.
35. Galileo’s observations showed that
A. Jupiter had moons going around it like a mini-Solar System.
B. the Milky Way consisted of billions of planets too faint to see with the naked eye
C. the Earth was indeed at the center of the Solar System.
D. telescopes were not yet good enough to be useful.
E. Saturn showed distinct phases like the Moon.
36. Ocean tides are caused primarily by
A. seismic pressure waves beneath the surface.
B. tectonic motion of the spreading ocean floor.
C. the Moon’s gravitational pull.
37. From Amherst, at latitude 42◦ N, Polaris hangs about
A. 18.5
B. 23.5
C. 42
D. sunlight reflecting off waves.
E. All of the above.
degrees above the northern horizon
D. 48
E. 52
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38. Acceleration is
A. the rate of speed of a body in motion
B. the effect of gravity
C. the variation of velocity of a body
D. the result of Newton’s Third Law
E. what prevents planets from falling into the Sun
39. What causes seasons here on planet Earth?
A. periodic changes in the heat retention of the Earth’s atmosphere.
B. The elliptical orbit of the Moon.
C. because of the alignment of the solar and lunar cycles.
D. The tilt of the Earth’s axis.
E. the Earth’s elliptical orbit brings it closer and farther from the Sun.
40. What is the wavelength (in meters) of electromagnetic radiation with frequency ν = 3.0 × 1014 Hz?
A. 1 meter
C. 10−6 meter
E. none of the above
B. 100 meter
D. light has no mass
41. What is the period of a comet if its average orbital radius is 4 AU? (hint: find Kepler’s Third Law among the
formulas above)
A. 1 yr
B. 2 yr
C. 4 yr
D. 8 yr
E. 16 yr
42. If the Earth were tipped 37◦ instead of 23.5◦ , seasons on Earth would be
A. much less severe
B. much more severe
C. much longer
E. hotter in the northern hemisphere, colder in the southern
D. much shorter
43. What is the energy of the photons with wavelength λ = 5800 × 10−10 meter?
A. Zero
B. 5800 Joule
C. 1/4
D. 3.4×10−19 erg
E. 3.4×10−19 Joule
44. A 100-Watt light bulb needs 100 Joule of energy every second to shine. How long such a light bulb could shine with
the energy liberated by converting 1 kg of mass into energy? Remember the famous formula E = m c2 ...
A. About 1 second
C. About 1 month
E. About 300 years
B. About 30 million years
D. About 1 year
45. How many different wavelengths are contained in the spectrum of blackbody radiation?
A. A large, but finite number.
B. An infinite number.
C. An infinite, but discrete number.
D. A finite and discrete number.
E. The blackbody radiation is black, hence has no wavelengths.
46. If we shine light on an atom, and the wavelength of the light has energy that does not match any energy difference
between the orbits of the electrons of that atom, what is going to happen?
A. Nothing, the atom simply ignores the light.
D. The atom gets de-excited.
B. The atom looses some of its electrons.
E. The atom reflects the light back.
C. The atom gets excited.
47. If a external force F is applied on a moving object perpendicular to the direction of motion, the total momentum
of that object
A. remains the same because total momentum is conserved.
B. changes by an amount proportional to 1/F 2 .
C. changes by an amount proportional to F .
D. the strength of the momentum remains the same, but its direction changes.
E. Both C and D.
Please answer the following survey questions:
48. This test was
A. much harder than
B. a little harder than
I expected.
C. about as hard as
D. a little easier than
E. a lot easier than
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49. The course has been
A. much harder than
B. harder than
I expected based on my impression after attending the first week.
C. as difficult as
E. much easier than
D. easier than
50. I would get more out of this course if the level were
A. much harder than
C. about the same as
B. harder than
D. easier than
it has been so far.
E. much easier than
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Key for exam1
1.
2.
3.
4.
5.
C
B
A
D
A
6.
7.
8.
9.
10.
D
D
A
D
C
11.
12.
13.
14.
15.
B
B
E
D
D
16.
17.
18.
19.
20.
E
E
B
A
A
21.
22.
23.
24.
25.
A
C
B
C
C
26.
27.
28.
29.
30.
A
B
D
C
C
31.
32.
33.
34.
35.
B
C
C
C
A
36.
37.
38.
39.
40.
C
C
C
D
C
41.
42.
43.
44.
45.
D
B
E
B
B
46. A
47. E