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Astronomy 101, Exam #2
Name___________________________________________________________________
No notes, No books; You can use calculators
c = 3 x 108 m/s
1 AU = 1.49 ×1011 meters
1 light year = 9.46 × 1015 meters
h = 6.626 x 10-34 J●s
G = 6.67 × 10-11 m3 kg-1 s-2
g = 9.8 m/s2
σ = 5.67 x 10-8 W m-2 K-4
mass of Earth = 5.97 × 1024 kg
mass of Moon = 7.35 x 1022 kg
radius of Earth = 6.38 × 106 m
1 nm = 1 x 10-9 meters
mass of Sun = 1.99 x 1030 kg
mass of Jupiter = 1.90 x 1027 kg
radius of Jupiter = 7.15 × 107 m
radius of Moon = 1.74 × 106 m
1) Why isn’t hydrogen fused into helium in the Sun’s convection zone?
A)
B)
C)
D)
E)
Hydrogen isn’t abundant enough.
The temperature is not hot enough.
The temperature is too hot.
Electrons are too abundant.
Helium is fused into carbon instead.
2) If it is -100o Celsius, what is the temperature in Kelvin?
A)
B)
C)
D)
E)
-73.15 Kelvin
173.15 Kelvin
473.15 Kelvin
673.15 Kelvin
883.15 Kelvin
3) In the Sun, 1 kg of hydrogen is fused into helium. In this scenario, which of these
statements is the most accurate?
A) 1 kg of helium is produced
B) 0.5 kg of helium is produced and 0.5 kg of the original mass is converted into
energy
C) 1 kg of the original mass is converted into energy
D) 0.872 kg of helium is produced and 0.128 kg of the original mass is converted
into energy
E) 0.993 kg of helium is produced and 0.007 kg of the original mass is converted
into energy
Astronomy 101, Exam #2
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4) A photon has a frequency of 1 x 1015 Hz. What is the wavelength of this photon?
A)
B)
C)
D)
E)
3 x 1023 meters
6.626 x 10-19 meters
3 x 107 meters
3.33 x 106 meters
3 x 10-7 meters
5) As the frequencies of photons of light increase, their …
A)
B)
C)
D)
E)
Wavelengths increase and their energies increase
Wavelengths decrease and their energies increase
Wavelengths decrease and their energies decrease
Wavelengths increase and their energies stay the same
Wavelengths stay the same and their energies stay the same
6) Which of the following objects has the most kinetic energy?
A) A 100 kg mass moving at 1 km/s.
B) A 20 kg mass moving at 2 km/s.
C) A 2 kg mass moving at 5 km/s.
D) A 10 kg mass moving at 4 km/s.
E) A 5 kg mass moving at 2 km/s.
7) The Homestake Gold Mine experiment was designed to detect neutrinos. What insight
can be gained from such an experiment?
A) The rate that visible light from the Sun is being absorbed by the Earth’s
atmosphere
B) The rate that hydrogen is being fused into helium in the Sun
C) The rate that gamma rays are hitting the Earth’s atmosphere
D) The rate that white dwarfs are being formed in the galaxy
E) The rate that stars form in the galaxy
8) A K5 star and a B3 star both have an apparent magnitude of +0.5 in the visible
wavelength region. Both stars are 144 light years from Earth. Which of these statements
is the most accurate to say?
A)
B)
C)
D)
E)
The K5 star will be twice as bright as the B3 star
The B3 star will be twice as bright as the K5 star
Both stars have the same surface temperature.
Both stars have the same luminosity.
Both stars are primarily composed of iron
Astronomy 101, Exam #2
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9) How many hydrogen atoms fuse to produce one helium atom?
A) 1
B) 2
C) 4
D) 5
E) 6
10) What is the frequency of a photon of light if the wavelength is 5 x 1029 meters?
6 x 1015 Hertz
1.5 x 10-36 Hertz
1.5 x 1037 Hertz
1.5 x 1036 Hertz
6 x 10-22 Hertz
A)
B)
C)
D)
E)
11) Luminosities of stars are usually given in units of …
A)
B)
C)
D)
E)
Newtons
Parsecs
Kilograms
Watts
Gauss
12) You take an image of the sky. On the image, a star has an apparent magnitude of +8,
a main-belt asteroid has an apparent magnitude of +6, a Kuiper Belt Object has an
apparent magnitude of +17, a Trojan asteroid has an apparent magnitude of +14, and
Pluto has an apparent magnitude of +15. Which object is faintest in the sky?
A)
B)
C)
D)
E)
The star
The main-belt asteroid
The Kuiper Belt Object
The Trojan asteroid
Pluto
13) What is the primary reason why so many telescopes are located on Mauna Kea?
A) They can be open 24 hours and 7 days of week
B) The telescopes are above a significant amount of the Earth’s atmosphere
C) You do not have to worry at all about the distorting effects of the Earth’s
atmosphere
D) Gamma-rays from stars can be observed on Mauna Kea
E) The telescopes are much close to the objects they will study
Astronomy 101, Exam #2
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14) Why are X-ray telescopes located in space and not on the surface of the Earth?
A)
B)
C)
D)
E)
X-rays are dangerous to humans.
X-rays cannot penetrate deep into the Earth’s atmosphere
X-rays tend to make the telescopes radioactive
X-rays pass through mirrors on Earth and are not detected
X-rays do not interact with silicon in mirrors properly on the surface of the
Earth
15) Somebody says that a spectrum of a star appears blueshifted. What is happening to
the star?
A)
B)
C)
D)
E)
The star is getting hotter
The star is getting colder
The star is moving towards you.
The star is moving away from you
The star is getting larger
16) A star is 20 light years from Earth. The star is moved so it is 10 light years from
Earth. How will the brightness of the star change as seen from Earth?
A)
B)
C)
D)
E)
The brightness will not change
The star will become twice as bright.
The star will become four times brighter
The star will become eight times brighter.
The star will become sixteen times brighter.
17) Different isotopes of an element have different numbers of …
A)
B)
C)
D)
E)
Neutrons
Protons
Isotopes
Neurons
Neutrinos
18) How much kinetic energy does a 1 kg ball with a velocity of 2 km/s have?
A) 4 x 106 Joules
B) 2 x 106 Joules
C) 2 Joules
D) 4 Joules
E) 2,000 Joules
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19) All the stars on the main sequence …
A)
B)
C)
D)
E)
Have the same brightness
Fuse hydrogen into helium as their primary energy source
Have the same temperature
Fuse helium into carbon as their primary energy source
Become black holes after they leave the main sequence
20) Put these parts of the electromagnetic spectrum in order from shortest wavelength to
longest wavelength:
Shortest  Longest wavelength
A)
B)
C)
D)
E)
Infrared, Radio, visible, ultraviolet, X-ray, gamma-ray
Gamma-ray, X-ray, ultraviolet, visible, infrared, radio
Radio, visible, ultraviolet, X-ray, gamma-ray, infrared
Radio, infrared, visible, ultraviolet, X-ray, gamma-ray
Radio, X-ray, infrared, ultraviolet, visible, gamma-ray
21) The hottest part of the Sun is the …
A)
B)
C)
D)
E)
Radiation zone
Convection zone
Photosphere
Corona
Core
22) As the temperature increases for an object, the peak of its blackbody radiation curve
measured for the object moves to …
A)
B)
C)
D)
E)
Lower intensities and longer wavelengths
Higher intensities and shorter wavelengths
Lower intensities and shorter wavelengths
Higher intensities and longer wavelengths
Does not change in intensity or in wavelength position
23) The temperature of the visible surface of the Sun is approximately …
A) 2,300 K
B) 100,000,000 K
C) 5,800 K
D) 4,100 K
E) 1,000 K
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24) What apparent magnitude in the visible wavelength region for a star makes it
impossible to see with the naked eye?
A)
B)
C)
D)
E)
-1.5
0
+1
+3
+8
25) Absolute zero has a temperature of …
A) 100o C
B) 0o C
C) 273.15o C
D) -273.15o C
E) -100o C
26) The densest part of the Sun is the …
A)
B)
C)
D)
E)
Radiation zone
Convection zone
Photosphere
Corona
Core
27) A prism can be used to break light up into its constituent spectral colors since
different wavelengths of light are refracted differently by glass and leave the prism at
different angles. What is the order of the colors of the light from smallest to highest
frequency?
Smallest  Highest frequency
A)
B)
C)
D)
E)
Violet, Indigo, Red, Blue, Green, Yellow, Orange
Red, Orange, Yellow, Green, Blue, Indigo, Violet
Red, Yellow, Orange, Blue, Green, Indigo, Violet
Violet, Indigo, Green, Blue, Orange, Yellow, Red
Violet, Indigo, Green, Yellow, Orange, Red, Blue
28) The Sun emits most of its radiation in what part of the electromagnetic spectrum?
A)
B)
C)
D)
E)
Gamma-ray
X-ray
Ultraviolet
Visible
Infrared
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29) What two wavelength regions do telescopes that are most commonly found on the
surface of the Earth observe in?
A) gamma and X-ray
B) visible and radio
C) gamma and ultraviolet
D) X-ray and infrared
E) X-ray and ultraviolet
30) Which of these parts of the electromagnetic spectrum has the shortest wavelength?
A)
B)
C)
D)
E)
Radio waves
X-rays
infrared
ultraviolet
visible
31) The most abundant element in the Sun is …
A) oxygen
B) silicon
C) carbon
D) hydrogen
E) helium
32) The Hertzsprung-Russell Diagram plots the luminosities and temperatures of …
A)
B)
C)
D)
E)
dwarf planets
planets
stars
asteroids
satellites
33) Put these stars in order from hottest to coldest surface temperatures: A3, B2, F7, K6,
M8.
Hottest  Coldest surface temperature
A) B2, A3, K6, F7, M8
B) M8, K6, F7, A3, B2
C) A3, B2, F7, K6, M8
D) B2, A3, F7, K6, M8
E) F7, B2, A3, M8, K6
Astronomy 101, Exam #2
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34) The term “blackbody” refers to an idealized object that …
A) is moving faster than the speed of light
B) absorbs all radiation incident on its surface and then emits radiation based on its
temperature..
C) is at a temperature of absolute zero and, therefore, appears black since it does not
emit any radiation
D) is formed from electrons ejected by a plasma
E) emits only radio waves when heated and only visible light when cooled
35) The atomic number of an element is equal to the number of ____________ that
are found in an atom of an element.
A) neutrons and electrons.
B) protons.
C) protons and neutrons.
D) protons and electrons.
E) neutrons.
36) Which of these spectral types has the longest lifetime on the main sequence?
A) B type
B) A type
C) K type
D) O type
E) F type
37) For main sequence stars, the general rule is that the lower the surface
temperature, …
A) the greater the size of the core
B) the greater the masses of the stars.
C) the less luminous are the stars.
D) the greater the diameter of the star
E) the shorter the lifetime on the main sequence
Astronomy 101, Exam #2
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38) What is the biggest advantage of putting a telescope on the Moon than on the
Earth?
A) The Moon-based telescope will be easier to fix.
B) The Moon-based telescope will be much closer to the objects in space that it
will it study.
C) You do not have to worry about the distorting effects of the Earth’s
atmosphere
D) The Moon-based telescope will be cheaper to build.
E) Your telescope on the Moon will not be struck by charged particles.
39) Which of these spectral types will have a surface temperature most similar to the
Sun?
A)
B)
C)
D)
E)
M5
M2
G2
B4
K3
40) What is the energy of a photon with a frequency of 5 x 106 Hz?
A)
B)
C)
D)
E)
3.313 x 10-30 Joules
1.9878 x 10-33 Joules
3.313 x 10-27 Joules
1.9878 x 10-25 Joules
1.9878 x 10-31 Joules