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ASTR 1000-001: The Solar System
Midterm Exam #2
March 31 2022
Test Form A
Solutions
Test Form B
has exactly the same questions, only with a different order for the multiple-choice
questions. Multiple-choice question answers for
Form B
:
AEAAC CACDA BCECC CAAAA
ACADC AAABA
Multiple-choice questions. Please use the Scantron sheet.
(2 points each; 60 points total)
1.
Which of the following is NOT a pattern of motion in our Solar System?
A.
Most planets rotate in the same direction they orbit.
B.
Most planetary orbits lie in the same plane.
C.
Most planets orbit in the same direction.
D.
Almost all large moons orbit their planet in the same direction as the planet's rotation.
E.
The planets orbit the Sun in a direction opposite that of the Sun's rotation.
2.
Which of the following is NOT correct about the exceptions to the patterns in the solar system
A.
Jupiter has an abnormally large moon Ganymede.
B.
Earth has an abnormally large moon comparing to its own size.
C.
Venus rotates in the opposite direction.
D.
Uranus rotates on its side.
3.
The
frost line
of the solar system was located approximately between
A.
the Sun and the present-day orbit of Mercury.
B.
the present-day orbits of Mercury and Venus.
C.
the present-day orbits of Mars and Jupiter.
D.
the present-day orbits of Venus and Earth.
E.
the present-day orbits of Uranus and Neptune.
4.
According to the nebular theory, what are asteroids and comets?
A.
leftover planetesimals that never accreted into planets
B.
chunks of rock or ice that condensed long after the planets had formed
2
C.
the shattered remains of collisions between moons
D.
the shattered remains of collisions between planets
5.
In essence, the
nebular theory
holds that
A.
our solar system formed from the collapse of an interstellar cloud of gas and dust.
B.
nebulae are clouds of gas and dust in space.
C.
the planets each formed from the collapse of its own separate nebula.
D.
the planets formed as a result of a near-collision between our Sun and another star.
6.
From center to surface, which of the following correctly lists the interior layers (defined by
density) of a terrestrial world?
A.
core, mantle, crust
B.
mantle, core, crust
C.
mantle, crust, core
D.
core, crust, lithosphere
7.
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around
planetesimals made of __________.
A.
only rocks and metals
B.
only ices
C.
rocks, metals, and ices rocks
8.
Which of the following
best
describes
differentiation
in planetary geology?
A.
Gravity separates molten materials according to density.
B.
Different types of minerals form a conglomerate rock.
C.
One planet's surface evolves differently from another planet's surface.
D.
One part of a planet's surface evolves differently from another part of the same
planet's surface.
9.
Which internal energy source is the most important in continuing to heat the terrestrial
planets today?
A.
accretion
B.
differentiation
C.
radioactivity
D.
tidal heating
10.
Which of the following is NOT a cooling process for planetary interiors:
A.
Convection
B.
Conduction
C.
Radiation
D.
Differentiation
11.
Which of the following best describes
convection
?
A.
Rocks sink in water.
B.
Warm material expands and rises while cool material contracts and falls.
C.
Warm material gets even warmer and cool material gets even cooler.
D.
A liquid separates according to density, such as oil and water separating in a jar.
3
12.
Volcanism is more likely on a planet that
A.
is closer to the Sun.
B.
is struck often by meteors and solar system debris.
C.
has high internal temperature.
D.
doesn't have an atmosphere or oceans.
13.
Which of the following
best
describes
tectonics
?
A.
the creation of bowl-shaped depressions by asteroids or comets striking a planet's
surface
B.
the eruption of molten rock from a planet's interior to its surface
C.
the disruption of a planet's surface by internal stresses
D.
the wearing down or building up of geological features by wind, water, ice, and other
phenomena of planetary weather
14.
Which of the following is NOT evidence of liquid water on ancient Mars:
A.
channels that look like dry riverbeds
B.
eroded crater rims
C.
Spirit
and
Opportunity
rovers have found mineral evidence of water
D.
Layered sedimentary rocks
E.
Large volcanic mountains
15.
What process has played the greatest role in determining the arrangement of the continents
on Earth?
A.
impact cratering
B.
volcanism
C.
plate tectonics
D.
erosion
16.
What is the
main
factor that makes Earth more geologically active than the other terrestrial
planets?
A.
It is larger, so it has retained its internal heat for longer.
B.
It is farthest from the Sun, so it receives less light.
C.
It has a large Moon, so it is heated by tidal forces.
D.
It has far more radioactive material than other planets.
E.
It formed much later than the other planets.
17.
Earth has a relatively strong magnetic field, but Mars does not. Which of the following probably
explains why Mars lacks a strong magnetic field today?
A.
It rotates too slowly
B.
It is too far from the Sun
C.
Its core is too cool for convection
D.
Its lithosphere is too thick.
18.
How are wavelength, frequency, and wave speed related for light waves?
A.
Longer wavelength means lower frequency
B.
Longer wavelength means higher frequency
C.
Longer wavelength means higher frequency
D.
Longer wavelength means lower frequency
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4
E.
There is no simple relationship because different light waves travel at different
speeds.
19.
Which statement about photons is
true
?
A.
An infrared photon has less energy than an x-ray photon, but travels at the same
speed.
B.
An infrared photon has less energy than an x-ray photon, and travels more slowly.
C.
An infrared photon has more energy than an x-ray photon, and travels more quickly.
D.
An infrared photon has more energy than an x-ray photon, but travels at the same
speed.
20.
A neutral oxygen isotope atom has 8 protons and 9 neutrons in the atomic nucleus. How
many electrons does it have?
A.
8
B.
6
C.
9
D.
17
21.
What do we mean when we say that
energy levels
are quantized in atoms?
A.
We mean that the photons can have only discrete values of electrical potential energy in
atoms.
B.
We mean that the photons can have only continuous values of electrical potential energy in
atoms.
C.
We mean that the electrons can have only discrete values of electrical potential energy in
atoms.
D.
We mean that the electrons can have only continuous electrical potential energy in atoms.
22.
The set of emission lines that we see in a star's spectrum depends on the star's:
A.
chemical composition.
B.
distance from us
C.
surface temperature
D.
interior structures
23.
Earth has a relatively strong magnetic field, but Mars does not. Which of the following probably
explains why Mars lacks a strong magnetic field today?
A.
It rotates too slowly
B.
It is too far from the Sun
C.
Its core is too cool for convection
D.
Its lithosphere is too thick.
24.
Thermal radiation
is defined as
A.
radiation produced by a hot object.
B.
radiation in the infrared part of the spectrum.
C.
radiation that depends only on the emitting object's temperature.
D.
radiation in the form of emission lines from an object.
25.
If a hydrogen emission line appears at 656 nm in the laboratory, what can we say about a
cloud of hydrogen gas, with an emission line at 680 nm?
A.
It is receding away from us.
5
B.
It is moving toward us.
C.
It is neither receding nor approaching us.
D.
There is not enough information to say anything about the cloud's motion.
26.
You observe the same spectral line in two stars that are identical in every way except that one
rotates faster than the other. How does the spectral line differ between the two?
A.
There is no difference.
B.
The line in the faster rotating star is blueshifted.
C.
The line in the faster rotating star is redshifted.
D.
The line in the faster rotating star is broader.
E.
The line in the faster rotating star is narrower.
27.
The pressure in the exosphere (highest layer) is
____ that in the troposphere (lowest layer) of Earth
A.
higher than
B.
lower than
C.
the same as
28.
Which of the following best describes how the
greenhouse effect
works?
A.
A planet's surface absorbs visible sunlight and returns this absorbed energy to space
as thermal radiation in infrared light. Greenhouse gases slow the escape of this
infrared radiation, which thereby heats the lower atmosphere.
B.
Greenhouse gases absorb X rays and ultraviolet light from the Sun, and this absorbed
radiation then heats the atmosphere and the surface.
C.
Greenhouse gases absorb infrared light coming from the Sun, and this absorbed
sunlight heats the lower atmosphere and the surface.
D.
The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light
and thereby makes the atmosphere much hotter than it would be otherwise.
29.
Why is the Coriolis effect so weak on Venus?
A.
because Venus rotates so slowly
B.
because Venus is so hot
C.
because Venus has such a thick atmosphere
D.
because Venus has such a strong greenhouse effect
30.
All of the following have occurred over long periods of time on Earth. Which one is
not
thought to have played a major role in long-term changes in Earth's climate?
A.
a gradual rise in the atmospheric content of oxygen
B.
changes in the Earth's axis tilt
C.
changes in the Earth's overall reflectivity
D.
changes in the atmospheric concentration of greenhouse gases
6
Written Questions
(40 points)
1. Layout, patterns, and formation of the Solar System (18 pts)
a)
Viewing from above the north pole, Earth orbits the sun in the counterclockwise direction. Does
Jupiter orbit the Sun in the clockwise or counterclockwise direction? Why? (4)
Counterclockwise direction. (2 pts)
Because the solar system is formed from a collapsed nebula, planets all orbit the Sun in the same
direction as the rotation of the nebula. (2 pts)
(1 pt for mentioning all planets orbit the sun in the same direction. 1pt for mention angular momentum
conservation)
b)
Name one exception to the patterns in the solar system. What may have caused that exception? (4)
Exceptions: Venus rotates backwards. Uranus rotates on its size. Earth has a abnormally large moon
comparing to its own size. (2 pts for name any one of the three)
They are all thought to be caused by the impact of a large object. (2 pts)
c)
Why are terrestrial planets in the inner solar system and Jovian planets in the outer solar system? (4)
Terrestrial planets are formed from accretion of planetesimals of solid rock and metal. During the
formation of the solar system, the temperature inside the frostline is so high that only rock and metal can
condensate to form solid particles and planetesimals. So terrestrial planets are all formed inside of the
frostline. (2 pts)
Jovian planets are from accretion of planetesimals of solid rock, metal, ice and other hydrogen
compounds, which eventually attracted and held large amount of hydrogen and helium gas around it with
its large gravity. Outside the frostline, it is cool enough for hydrogen compounds (including H
2
O), in
addition to rock and metal, to condensate to form solid particles and planetesimals. So Jovian planets are
all formed outside the frostline. (2 pts)
(Full credit for stating metal and rock can condensate inside the frostline and water can only condensate
outside the frostline. 2 pts for mentioning inside and outside the frostline)
d)
Name one of the interior heating processes for terrestrial planets. Describe how it works and what the
energy conversion is. (6)
•
Accretion: During the process of accumulating mass from planetesimals, the gravitational potential
energy from the colliding planetesimals is converted to kinetic energy and then to the thermal energy
that heats the planetary interior.
•
Differentiation: During the process of denser material sinking and less-dense material rising, there is a
net loss of gravitational energy that is converted to thermal energy, i.e. the interior heat of the planet.
•
Radioactive decay: The radioactive isotopes in the rock and metal decay spontaneously, during which
the atomic nucleus of the isotopes breaks into two or more particles, some particles are ejected with
high speed, and electromagnetic waves are emitted. The planetary interior is heated by colliding with
the ejected high-speed particles and absorbing the electromagnetic waves. The mass-energy stored in
the isotopes is converted to kinetic energy and radiative energy and eventually to the thermal energy
of the planetary interior.
(2 pts for naming of one of the three. 2 pts for describing the process. 2 pts for for getting the energy
conversion correct.
accretion: gravitational energy or kinetic energy
à
thermal energy; differentiation: gravitational
potential energy
à
thermal energy; radioactive decay: mass-energy
à
thermal energy)
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7
2. Light-matter interactions
(22 pts)
a)
What kind of wave is light? (2)
Electromagnetic waves.
(1 pt for mentioning magnetic or electric fields)
b)
Why does the sky look blue? Why does Mars look red? (4)
The atmosphere scatters a lot of blue light from Sun into all random directions, so wherever we look
into the sky it appears blue. (2 pt)
(1 pt for mentioning atmosphere)
Mars look red because it reflects mostly red light from the Sun. (2 pts)
c)
How can we tell the surface temperature of the Sun? Is a blue star hotter or colder than the Sun?
Why? (6)
From its thermal radiation spectrum. (2 pts)
The blue star is hotter. (2 pts)
The fact that the stars is blue comparing to the Sun that is white means the average frequency of its
thermal radiation is higher (or the average wavelength is shorter) than the Sun, which tells us it is
hotter than the Sun. (Or the more blueish the hotter, the more redish the colder) (2 pts)
d)
One of the hydrogen absorption lines is 656.3 nm (wavelength). This absorption line corresponds to
an electron in the hydrogen atom jumping from energy level 2 to energy level 3 by absorbing a
photon. What are the frequency and energy of the absorbed photon? (The frequency is 4.6 x 10
14
Hz,
and the energy is 1.9 eV. But you need to show the calculation) (6)
Wave speed = wavelength x frequency
(1 pt)
Unit conversion: Wave length = 656.3 nm = 6.563 x 10
-7
m
(0.5 pt)
Frequency = wave speed/wave length
(1 pt)
= (3 x 10
8
m/s)/(6.564 x 10
-7
m)
(1 pt)
= 4.6 x 10
14
s
-1
Unit conversion: 4.6 x 10
14
s
-1
= 4.6 x 10
14
Hz
(0.5 pt)
Energy of the absorbed photon: E = h x frequency
(1 pt)
= 6.6 x 10
-34
J x Hz
-1
x 4.6 x 10
14
Hz
(0.5 pt)
= 3.04 x 10
-19
J
Unit conversion: 3.04 x 10
-19
J = 3.04 x 10
-19
/1.6 x 10
-19
eV = 1.9 eV
(0.5 pt)
(full credit as long as using the right formulas, plugging in the right numbers, and converting units
correctly. Don’t deduct points for carrying over any purely numeric mistake)
e)
Is the average distance between the electron at level 3 and the atomic nucleus larger or smaller than
that of level 2? The energy of level 2 is 10.2 eV. What is the energy of level 3? (4)
Larger. (2 pts)
(The electron at level 3 has higher electrical potential energy than level 2, which means it is father
away from the atomic nucleus.)
The energy of level 3 is 1.9eV higher than that of level 2 according to the result from (d).
So the energy of level 3 is: 10.2 eV + 1.9 eV = 12.1 eV
( 2 pts)
(1 pt for mentioning the energy at level 3 is higher)