Physics 111 - Astronomy & Space Physics -
Spring 2000
Exam 1 - Key
Please note: The answer key shown below is
for FORM 1 of the exam. If you had FORM 2, please refer to the SCRAMBLE
FORM which indicates which questions on FORM 2 are the equivalent questions
on FORM 1. I agree that this is an unnecessary and bothersome
exercise, but it is beyond my control.
February
7, 2000
S.D.
Marcum
Astronomy & Space Physics
EXAM
1 - ***FORM 1***
Name
__________________________
INSTRUCTIONS: Fill
in your Student ID# and the FORM NUMBER of your
exam
on the answer sheet. Choose
the BEST answer for each question and
mark
your choice on the answer sheet. Use
a #2 pencil only.
1.
On a given evening, you notice that the sunlit portion of the Moon
has
a crescent shape. This simple observation tells you
a.
nothing at all about the position of the Moon in space compared
to
that of Earth and the Sun.
b.
that the Moon is further from the Sun than is the Earth at that
time.
*c.
that the Moon is closer to the Sun than is the Earth at that
time.
d.
that the line from the Earth to the Moon is exactly at right
angles
to the Sun-Earth line.
2.
Which of the following statements correctly states the significance
of
Galileo's observation that Venus shows phases?
a.
The phases were interesting, but did not have any particular
significance
other than that.
b.
Since the phases were not correlated with angular size, they
actually
supported the geocentric theory more than the
heliocentric
theory.
*c.
The phases were correlated with angular size in a way that
supported
the heliocentric theory.
d.
The phases showed that, like the Moon, Venus is always much
closer
to the Earth than is the Sun.
3.
Suppose an asteroid is discovered with an elliptical orbit, a period
of
exactly 1 year, and perihelion 0.5 AU from the Sun. Using
Kepler's
third law, how far from the Sun is this asteroid when at
aphelion?
(Drawing a diagram of the orbit, including the Sun, will
help.)
*a.
1.5 AU
b.
1.0 AU
c.
2.0 AU
d.
2.5 AU
4.
As the Earth rotates, the point above the head of a person (the
zenith)
standing on the equator sweeps out along
a.
a path between north and south poles, along a great circle.
b.
the ecliptic plane.
*c.
the celestial equator.
d.
a variable path across the sky within the region of the zodiac,
but
not always on the celestial equator.
5.
A comet is observed to return to the vicinity of the Sun on a long
elliptical
orbit with a period of 31.7 years. What is the semimajor
axis
of its orbit?
*a.
10 AU
b.
31.7 AU
c.
1000 AU
d.
178.5 AU
6.
Tycho Brahe
a.
improved the refracting telescope, which allowed him to extend
Galileo's
observations of the sky.
b.
developed a reflecting telescope, which used a curved mirror to
focus
the light.
c.
developed the first detailed heliocentric model for the solar
system,
which replaced the geocentric model of Ptolemy.
*d.
made accurate measurements of planetary positions, which Kepler
later
used to find the shapes of planetary orbits.
7.
If light from a hot, dense star passes through a cool cloud of gas,
a.
the whole spectrum will be reduced in intensity.
*b.
only specific wavelengths of light will be removed from the
spectrum.
c.
the atoms of the gas cloud will add energy to the overall
spectrum,
enhancing it at specific wavelengths to produce
emission
lines.
d.
the cool gas will not affect the spectrum of the star, since cool
atoms
cannot absorb light.
8.
In modern astronomy, the constellations are
*a.
88 sky regions covering the whole sky.
b.
a small number of well-defined groups of stars in our sky.
c.
12 specific regions through which the planets and Moon appear to
move
in our sky.
d.
specific patterns of stars that point to certain directions,
useful
for navigation.
9.
The specific colors of light emitted by an atom in a hot, thin gas
(e.g.,
in a neon tube, a fluorescent bulb or a gas cloud in space)
are
caused by
*a.
electrons jumping to lower energy levels, losing energy as they
do
so.
b.
the vibrations of the electrons within the atom.
c.
protons jumping from level to level.
d.
an electron dropping into the nucleus, producing small nuclear
changes.
10.
A particular photon of ultraviolet (UV) light has a wavelength of
200
nm and a photon of infrared (IR) light has a wavelength of 2000
nm.
What is the energy of the UV photon compared to the IR photon?
a.
It has 1/10 of the energy of the IR photon.
b.
It has 100 times more energy than the IR photon.
*c.
It has 10 times more energy than the IR photon.
d.
It has 1/100 of the energy of the IR photon.
11.
The Earth exerts a force on you as you stand on its surface. What is
the
size of the force exerted on the Earth by you, when compared to
the
above force?
a.
Twice as large, because of the Earth's rotation.
b.
Zero, you do not exert a force on the Earth.
c.
Very small, because your mass is small compared to that of Earth.
*d.
The same.
12.
Which of the following parameters will dictate whether a particular
solar
eclipse appears as a total or an annular eclipse to an
observer
on the center-line of the Moon's shadow?
a.
The distance of the Earth from the Sun at the time of eclipse.
*b.
The distance of the Moon from the Earth at the time of eclipse.
c.
The time of day or night.
d.
The phase of the Moon, whether it is new, quarter or full.
13.
Suppose an astronomical satellite observes the Orion Nebula at a
wavelength
of 1250 nm. In what wavelength range is this satellite
observing?
a.
ultraviolet
*b.
infrared
c.
visible light
d.
x rays
14.
A full Moon will always be at its highest in our sky at about
*a.
midnight.
b.
sunrise.
c.
sunset.
d.
midday.
15.
How much of the total surface of the Moon is illuminated by the Sun
when
it is at quarter phase?
a.
all of it
b.
very little
c.
one quarter
*d.
one half
16.
If the Sun passes directly over your head on at least one day per
year,
then you are standing
a.
anywhere on the Earth (no limitation).
b.
exactly on the equator.
c.
within 66 1/2 of the equator.
*d.
within 23 1/2 of the equator.
17.
According to the heliocentric theory, which of the following objects
can
never transit (pass in front of) the Sun as seen from the Earth?
*a.
Mars
b.
Venus
c.
the Moon
d.
Mercury
18.
The Sun's apparent path across our sky against the background stars
(that
would be seen if the daylight sky were not light) is known as
a.
the great circle.
*b.
the ecliptic.
c.
the celestial equator.
d.
the celestial meridian.
19.
A small particle of interplanetary material is heated by friction
from
a temperature of 400K to 4000K as it falls into the atmosphere
of
the Earth and produces a meteor or a shooting star in our sky. If
this
object behaves like a perfect black body over this short time,
how
will its emitted radiation change as it is heated?
*a.
Its total emitted intensity will rise by a factor of 10,000 while
its
peak wavelength will become shorter by a factor of 10, from
infrared
to red visible light.
b.
Its total intensity will rise by a factor of 10, while its peak
wavelength
will become shorter by a factor of 10, moving from
infrared
to red visible light.
c.
Its total intensity will rise by a factor of 10,000 while its
peak
wavelength will become longer by a factor of 10, moving from
visible
to infrared or heat radiation.
d.
Its intensity will rise by a factor of 100 while the peak
wavelength
of emitted light will become shorter by a factor of
100,
moving from infrared to ultra-violet.
20.
A major contribution of Ptolemy to the development of astronomy was
to
*a.
derive a mathematical model for the solar system, in which
planets
move in epicycles and the epicycles orbited the Earth.
b.
originate the idea of a geocentric (Earth-centered) cosmogony,
that
was later developed mathematically by Aristarchus.
c.
derive a mathematical model for the solar system, in which
planets
move around the Earth in elliptical orbits, moving
fastest
when closest to the Earth.
d.
derive a mathematical model for the solar system, in which
planets
move around the Sun in circular orbits.
21.
How does the wavelength of visible light compare to the wavelengths
of
other forms of electromagnetic radiation?
*a.
Longer than x rays but shorter than radio waves.
b.
Longer than infrared but shorter than radio waves.
c.
Longer than x rays but shorter than gamma rays.
d.
Longer than ultraviolet but shorter than x rays.
22.
The phenomenon of parallax is
a.
the apparent change in angular size of an object as it moves
towards
or away from an observer.
*b.
the change in apparent position of a nearby object as the
observer
moves, compared to background objects.
c.
the change in direction of motion of a planet from retrograde to
direct
motion.
d.
the change in the apparent position of an object compared to
background
objects, as a result of the motion of the object.
23.
The Earth's atmosphere is transparent to which of the following
types
of electromagnetic radiation?
*a.
Radio waves.
b.
x rays.
c.
Short ultraviolet wavelengths.
d.
Long infrared wavelengths.
24.
Planets move past the background stars as seen by someone on the
Earth.
What is the normal direction of this motion?
*a.
From west to east because of the motion of the planet along its
orbit.
b.
From east to west because of the motion of the planet along its
orbit.
c.
From west to east because of the motion of the Earth along its
orbit.
d.
From east to west because of the rotation of the Earth.
25.
The spectrum of a star shows an equivalent set of dark absorption
lines
to those of the Sun, with one exception. Every line appears at
a
slightly longer wavelength, shifted toward the red end of the
spectrum.
What conclusion can be drawn from this observation?
a.
The temperature of the star's surface is higher than that of the
Sun.
*b.
The star is moving rapidly away from Earth.
c.
A cloud of cold gas and dust surrounds the star and is absorbing
light
from it.
d.
The star is moving rapidly toward the Earth.
26.
1 arc second is equal to
a.
1/60 of a full circle.
b.
1/360 of a full circle.
*c.
1/3600 degree.
d.
1/60 degree.
27.
The concept called "Occam's Razor" tells us that
a.
when two theories describe the same phenomena equally accurately,
always
choose the theory with the greater complexity.
b.
the theory that describes phenomena more accurately is more
likely
to be correct.
*c.
when two theories describe the same phenomena equally accurately,
always
choose the simpler theory.
d.
the theory that is applicable to the greatest range of phenomena
is
more likely to be correct.
28.
Which of the following factors makes it far more likely that a
person
will have seen a total lunar eclipse than a total solar
eclipse?
*a.
A total lunar eclipse can be seen by people on most of the
nighttime
side of Earth while a specific total solar eclipse can
only
be seen by people within a narrow strip of the Earth's
surface.
b.
A total lunar eclipse occurs at full Moon when the Moon is bright
and
high in the sky while a total solar eclipse occurs at new
Moon
when the Moon is dark and low in the sky.
c.
Total solar eclipses occur much less frequently than total lunar
eclipses.
d.
The Moon appears brighter during a total lunar eclipse than does
the
Sun during a total solar eclipse.
29.
A necessary condition for lunar or solar eclipses is that
a.
the Sun be on the celestial equator.
b.
the Sun be on or close to the ecliptic plane.
c.
the Earth be on the celestial equator.
*d.
the Moon be close to or crossing the ecliptic plane.
30.
The dark absorption lines in the solar spectrum are caused
a.
solely by absorption by atoms and molecules in the Earth's cool
atmosphere.
b.
by a hotter layer of gas that overlies the cooler solar surface,
and
that produces the absorption lines.
c.
by a cooler layer overlying the hot solar surface, consisting
solely
of hydrogen gas that produces all the absorption lines.
*d.
by a cooler layer of gas overlying the hot solar surface, that
contains
many elements including H, He, Mg, Ca, Fe, etc.
31.
If our daytime sky were not so bright, how fast would we see the Sun
move
across our sky with respect to the stars, as it moves through
one
full circle in one year?
a.
Exactly 24 per day or 1 per
hour.
b.
About 15 per hour.
*c.
About 1 per day.
d.
The Sun would never appear to move with respect to the stars in
the
sky.
32.
The contribution of Copernicus to the development of astronomy was a
mathematical
model for
a.
a heliocentric cosmogony in which the planets move in elliptical
orbits.
b.
a geocentric cosmogony in which the planets move in circular
epicycles.
c.
the solar system in which the gravitational force from the Sun
holds
the planets in their orbits.
*d.
a heliocentric cosmogony in which the planets move in circular
orbits.
33.
Which of the following "planets" will never be seen from Earth as a
crescent?
a.
the Moon
b.
Venus
*c.
Mars
d.
Mercury
34.
Which of the following statements correctly describes why Copernicus
decided
that the orbits of Mercury and Venus are smaller than the
orbit
of the Earth?
a.
Both planets occasionally pass through conjunction with the Sun,
as
seen from the Earth.
b.
Both planets show a complete cycle of phases, like the Moon.
c.
Both planets can sometimes be seen high in our sky at midnight.
*d.
Both planets stay fairly close to the Sun in our sky.
35.
As a newly formed star continues to contract, its temperature
increases
while the chemical nature of the gas does not change. What
will
happen to the peak wavelength of its emitted radiation?
*a.
It will move toward shorter wavelengths (e.g., IR to visible).
b.
It will not change, since it is not dependent on temperature.
c.
It will move toward longer wavelengths (e.g., visible to IR).
d.
It will remain constant, since the chemical state of the gas does
not
change.
36.
How much of the overall sky is above the celestial equator, i.e. in
the
northern hemisphere?
a.
More than one half, because of the precession of the poles.
*b.
Exactly one half.
c.
All of it, by definition.
d.
Less than one half, because of the tilt of the equator to the
ecliptic
plane.
37.
Which of the following statements about an asteroid moving in a
circular
orbit around the Sun is UNTRUE?
a.
It is accelerating.
b.
It is moving at a constant speed.
c.
It is moving in a flat plane.
*d.
It is moving at a constant velocity.
38.
An observer on the equator, in a period of one year, would be able
to
see what fraction of the overall sky?
a.
a variable amount, depending upon which year
b.
50%
*c.
100%
d.
a variable amount, depending upon the person's longitude
39.
How much gravitational force acts on an astronaut in the Space
Shuttle
in a circular orbit 300 km above the Earth's surface?
*a.
Almost (but not quite) as much as when the astronaut is standing
on
the surface of the Earth.
b.
Exactly the same as when the astronaut is standing on the surface
of
the Earth.
c.
Zerothe astronaut is weightless.
d.
Almost zero, but not quite.
40.
After reading the news items posted on the web for Phy 111 A concerning
Mars
Polar Land it
a. can
be concluded that it crashed into the surface of Mars and is a
total
loss.
b.is
clear that it is alive and well, but with too little radio power to
communicate
with ground controllers on Earth.
c.has
been determined that it fell into a deep canyon near Mars’ south
pole
and was destroyed.
*d. is
not yet clear whether or not it is still operating.
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