Astronomy Ch 4-7
Suppose two objects are attracting each other gravitationally. If you double the distance between them, the strength of their gravitational attraction __________.
decreases by a factor of 4 Gravity follows an inverse sqaure law with distance, so doubling the distance between them decreases the strength of the attraction by a factor of 22 = 4.
The James Webb Space Telescope is designed primarily to observe __________.
infrared light Its location in space allows it to observe infrared wavelengths that do not penetrate our atmosphere to the ground.
As long as an object is not gaining or losing mass, a net force on the object will cause a change in
velocity.
Which of the following statements about thermal radiation is always true?
A hot object emits more total radiation per unit surface area than a cool object.
Which of the following statements about thermal radiation is always true?
A hot object emits photons with a higher average energy than a cool object.
According to what we now know from Newton's laws, which of the following best explains why Kepler's second law is true?
A planet's angular momentum must be conserved as it moves around its orbit.
Which of the following statements about electrical charge is true?
A positive charge and a negative charge will attract each other.
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
A radio telescope and an optical telescope of the same size have the same angular resolution.
False
Atomic nuclei consist of protons and electrons.
False
Doubling the distance between two objects halves the gravitational force between them.
False
Electrons orbit an atomic nucleus like planets orbit the Sun.
False
Improvements in technology will eventually allow the entire electromagnetic spectrum to be observed from high mountaintop observatories.
False
Process of Science: Gravity only affects very massive objects and we can therefore only test theories about it when looking at the orbits of planets.
False
Speed and velocity are the same thing.
False
The greater the wavelength of light, the greater its energy.
False
There is no gravity in space.
False
When energy is converted from one form to another, a tiny amount is inevitably lost.
False
In the formula E = mc2, what does E represent?
the mass-energy, or potential energy stored in an object's mass
As a giant cloud of gas collapses due to gravity, you would expect its rate of rotation to -decrease -increase -stay unchanged
Increase this is a consequence of the law of conservation of angular momentum.
The frequency of a wave is
-measured in cycles per second. -the number of peaks passing by any point each second. -measured in hertz (Hz). -equal to the speed of the wave divided by the wavelength of the wave.
Absolute zero is
0° Kelvin
How much more light does an 8-meter telescope gather than a 2-meter telescope?
16 times as much Light-collecting area depends on the square of the telescope mirror diameter. Because an 8-meter telescope has 4 times the diameter of a 2-meter telescope, its light-collecting area is 42 = 16 times as great.
An atom of the element iron has an atomic number of 26 and an atomic weight of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
26 protons, 30 neutrons, 26 electrons
The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
30 m/s
Standing on the surface of the Earth you drop a rock down a well and it falls for 5 seconds before hitting the bottom. How fast is it moving when it hits the bottom of the well? Neglect air resistance.
50 m/s
Of the temperature ranges below, which range represents the smallest range of actual temperature?
50-100° Fahrenheit
If your mass is 60 kg on Earth, what would your mass be on the Moon?
60 kg
If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits
81 times more energy.
Which of the following represents a change from potential energy to kinetic energy? -A rock starting from rest on a high cliff, then moving faster and faster as it falls. -A kicked ball rising higher in the air and momentarily coming to rest at the top of its trajectory. -A car applying its brakes on a straight road and heating up the brake pads as it slows. -Sunlight melting a tray of ice.
A rock starting from rest on a high cliff, then moving faster and faster as it falls. The law of conservation of energy tells us that energy is conserved as the rock falls, so as it loses gravitational potential energy (by losing altitude) it gains kinetic energy (by increasing its speed).
When an atom absorbs a photon containing energy, any of the following can happen except which?
An electron moves from an upper energy level to a lower one
What celestial coordinate tells you how far north or south the celestial object is located in the sky?
Declination
According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?
Earth's orbit would not change.
Which of the following statements about electrons is not true?
Electrons orbit the nucleus rather like planets orbiting the Sun.
How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?
Four times
How does the Space Shuttle take off?
Hot gas shoots out from the rocket and, by conservation of momentum, the shuttle moves in the opposite direction.
What does the technique of interferometry allow?
It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
Why is Newton's version of Kepler's third law so useful to astronomers?
It can be used to determine the masses of many distant objects.
Where does the energy come from that your body uses to keep you alive?
It comes from the foods you eat.
What is meant by spectral resolution?
It is a measure of how close two spectral lines can be distinguished.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
What is meant by the resolution of an optical device?
It is the ability of an object fo form distinct images of two close objects
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion, and how many electrons will the ion have?
It must be ionized five times; it now has three electrons
How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
It releases a photon equal in energy to its own energy drop.
What would happen if the Space Shuttle were launched with a speed greater than Earth's escape velocity?
It would travel away from Earth into the solar system.
What do astronomers mean by light pollution?
Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
How are wavelength, frequency, and energy related for photons of light?
Longer wavelength means lower frequency and lower energy.
As you watch the video, notice that the size of the tidal bulges varies with the Moon's phase, which depends on its orbital position relative to the Sun. Which of the following statement(s) accurately describe(s) this variation?
Low tides are lowest at both full moon and new moon. High tides are highest at both full moon and new moon As the video shows, the tidal bulges are largest and the tidal minima are smallest at full moon and new moon. Those are the times when the tidal forces of the Sun and Moon align (and therefore add to one another). Therefore, high tides are higher and low tides are lower at these times, which are called spring tides. (In contrast, we have neap tides at first- and third-quarter moons, when high tides are not as high and low tides are not as low.)
Which of the following statements about X rays and radio waves is not true?
Neither X rays nor radio waves can penetrate the earth's atmosphere.
The fact that the Voyager spacecraft continues to travel out of the solar system, even though its rockets have no fuel, is an example of
Newton's first law of motion.
Earth has two tidal bulges at all times. Approximately where are these bulges located? One is over the Atlantic Ocean, and one is over the Pacific Ocean. One faces the Moon and one faces the Sun. Both are on lines perpendicular to the Earth-Moon line. One faces the Moon and one faces opposite the Moon.
One faces the Moon and one faces opposite the Moon. The tidal bulges face toward and away from the Moon, because they are caused primarily by the gravitational attraction between Earth and the Moon. Friction explains why the bulges are slightly ahead of the Earth-Moon line, rather than directly on the Earth-Moon line. We'll ignore that detail for now.
What celestial coordinate tells you how far east or west a celestial object is in the sky?
Right Ascension
The twinkling of stars is caused by:
motion of air in our atmosphere.
What is meant by refraction of light?
The Bending of light as it passes from one transparent medium to the next.
We only see one face of the Moon from Earth because
The Moon is already tidally locked to the Earth.
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic weight?
The atomic number is 79, and the atomic weight is 197.
Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
The blue star has a hotter surface temperature than the red star.
When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy?
The energy goes to producing sound and to heating the ground, rock, and surrounding air.
If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?
The one with the large redshift is moving away from us faster than the one with the small redshift.
You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?
The galaxy is moving away from you
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. If it is doubly ionized, what is the charge of the gold ion and how many electrons remain in the ion?
The gold ion has a charge of +2 and 77 electrons
Suppose that two stars are separated in the sky by 0.01 arcsecond, and you observe them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
The light from the two stars will be blended together so that they look like one star. A telescope with an angular resolution of 1 arcsecond can only distinguish two stars if they are separated by an angle greater than 1 arcsecond in the sky. Otherwise, the light of the two stars will be blended together so they appear as one.
Which of the following determines the image quatlity of a telescope?
The light-collecting abliblty and angular resolution
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?
The line in the faster rotating star is broader.
One tidal bulge faces toward the Moon because that is where the gravitational attraction between Earth and the Moon is strongest. Which of the following best explains why there is also a second tidal bulge?
The second tidal bulge arises because gravity weakens with distance, essentially stretching Earth along the Earth-Moon line. Tides are created by gravity, and the tidal force is caused by the fact that gravity weakens with distance. Therefore, the parts of Earth that are closer to the Moon feel a stronger gravitational attraction to the Moon, and the parts of Earth that are farther away feel a weaker gravitational attraction to the Moon. This varying gravitational attraction essentially stretches Earth along the Earth-Moon line, creating tidal bulges on both sides.
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?
The star is moving away from us.
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?
The star is moving toward us.
If we observe one edge of a star to be redshifted and the opposite edge to be blueshifted, what can we conclude about the star?
The star is rotating.
X-rays always have more energy than radio waves.
True
You are currently emitting electromagnetic waves.
True
We can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one?
The total amount of light in the spectrum tells us the star's radius.
Which of the following statements correctly describes the law of conservation of energy?
The total quantity of energy in the universe never changes.
Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?
The two stars will look like a single point of light.
In considering the Earth-Moon system we find
There are tidal forces on the Earth caused by the Moon There are tidal forces on the Moon caused by the Earth There are tidal forces on the Earth and Moon caused by the Sun, but the Sun's tidal influence is less than the Earth's on the Moon or the Moon's on the Earth.
Which of the following is always true about images captured with X-ray telescopes?
They are always displayed in false color.
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are NOT the true colors of the objects that were photographed.
If an astronaut goes on a space walk outside the Space Station, she will quickly float away from the station unless she has a tether holding her to the station. Choose the correct explanation why does the statement make sense (or is clearly true) or does not make sense (or is clearly false). This statement is false. She and the Space Station have different orbits at the beginning but will stay together due to mutual gravity. This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart. This statement is true. She and the Space Station cannot share the same orbit and will move apart quickly. This statement is true. She and the Space Station have different orbits at the beginning and will move apart.
This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart.
Which of the following best describes the origin of ocean tides on Earth? Tides are caused by the 23 1/2° tilt of the earth's rotational axis to the ecliptic plane. The Moon's gravity pulls harder on water than on land, because water is less dense than rock. Tides are caused on the side of Earth nearest the Moon because the Moon's gravity attracts the water. Tides are caused primarily by the gravitational force of the Sun. Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth.
Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth.
If you are driving at 30 miles per hour and increase your speed to 60 miles per hour, you quadruple your kinetic energy.
True
Lines of a particular element appear at the same wavelength in both emission and absorption line spectra
True
Part complete The energy levels for electrons vary from one element to another.
True
The Moon is constantly falling toward Earth.
True
The Moon is slowly moving away from Earth.
True
The atomic nuclei of the same element always have the same number of protons.
True
The center of mass for Earth orbiting the Sun lies inside the Sun.
True
The shorter the wavelength of light, the higher its frequency.
True
X rays from astronomical objects can only be detected from telescopes in space.
True
Which of the following scenarios correctly demonstrates the transformation of mass into energy as given by Einstein's equation, E = mc2?
When hydrogen is fused into helium, whether in the Sun or in a nuclear bomb, the mass difference is turned into energy.
Which of the following statements about X rays and radio waves is not true?
X rays travel through space faster than radio waves.
What is the primary reason that we launch X-ray telescopes into space rather than building them on the ground?
X-rays from space do not reach the ground. In fact, most forms of light do not reach the ground, with visible and radio waves as the major exceptions.
Most people are familiar with the rise and fall of ocean tides. Do tides also affect land?
Yes, though land rises and falls by a much smaller amount than the oceans. Tides affect the entire Earth, but they are much more noticeable for the oceans because water flows so much more easily than land. Still, the land rises and falls about 1 centimeter with the tides.
Kepler's second law of planetary motion
a planet moves faster in the part of its orbit nearer the Sun and slower when farther from the Sun, sweeping out equal areas in equal times.
How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?
a positive charge of +1
Part complete A perfectly opaque object that absorbs all radiation and reemits the absorbed energy as thermal radiation is
a thermal emitter.
Compared to the volume of its nucleus, the volume of an atom is about
a trillion times greater.
When white light passes through a cool cloud of gas, we see
an absorption line spectrum.
If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces
an emission line spectrum.
Newton's first law of motion
an object moves at constant velocity if there is no net force acting upon it.
What are the two most important properties of a telescope?
angular resolution light-collecting area The two most important properties of a telescope are its light-collecting area, which determines how faint of objects it can detect, and its angular resolution, which determines the sharpness of its images.
You have found that tides on Earth are determined primarily by the position of the Moon, with the Sun playing only a secondary role. Why does the Moon play a greater role in causing tides than the Sun?
because the gravitational attraction between Earth and the Moon varies more across Earth than does the gravitational attraction between Earth and the Sun The Sun exerts a stronger gravitational force on Earth, which is why Earth orbits the Sun. However, tides are caused by the variation in the gravitational attraction across Earth. Even though the gravitational attraction between Earth and the Moon is smaller than the attraction between Earth and the Sun, the Moon's much closer distance makes this attraction vary more across Earth. That is why tides are due primarily to the Moon, with only a secondary effect from the Sun.
What causes stars to twinkle?
bending of light rays by turbulent layers in the atmosphere
At which lunar phase(s) are tides least pronounced (e.g., the lowest high tides)?
both first and third quarters
At which lunar phase(s) are tides most pronounced (e.g., the highest high tides)?
both new and full Moons
Gasoline is useful in cars because it has
chemical potential energy.
A skater can spin faster by pulling her arms closer to her body or spin slower by spreading her arms out from her body. This is due to
conservation of angular momentum
Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will
continue to move in the same way until it is acted upon by a force.
If our eyes were sensitive only to X rays, the world would appear __________.
dark because X-ray light does not reach Earth's surface Because X rays from the Sun do not reach Earth's surface, eyes that were sensitive only to X rays would have nothing to see.
According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will
decrease by a factor of 9.
If an object's velocity is doubled, its momentum is
doubled.
Which of the following is an example in which you are traveling at constant speed but not at constant velocity?
driving around in a circle at exactly 100 km/hr
The allowed shapes for orbits under the force of gravity are
ellipses, parabolas, and hyperbolas.
When an electron in an atom goes from a higher energy state to a lower energy state, the atom
emits a photon of a specific frequency.
Radiative energy is
energy carried by light.
Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
extreme infrared
Newton's third law of motion
for any force, there is an equal and opposite reaction force.
Newton's Second Law of Motion
force = mass x acceleration
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma rays, X rays, ultraviolet, visible light, infrared, radio
The spectra of most galaxies show redshifts. This means that their spectral lines
have wavelengths that are longer than normal.
Compared to red light, blue light has higher frequency and
higher energy and shorter wavelength than red light.
Which of the following objects is not a close approximation of a thermal emitter?
hot, thin gas
Where should you put a telescope designed for ultraviolet observations?
in Earth orbit
If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?
in space While visible light can be observed from the ground, ultraviolet light can be easily observed only from space. Indeed, the capability of observing ultraviolet light is a major advantage of the Hubble Space Telescope over larger ground-based telescopes.
According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
increase by a factor of 4.
According to the universal law of gravitation, the force due to gravity is
inversely proportional to the square of the distance between objects.
When an atom loses an electron, it becomes
ionized
The loss of an electron from a neutral helium atom results in
ionized helium
Compare the light collecting ability of a telescope with an 8 inch diamter primary objective telescope to that of a telescope with a two inch primary objective.
it is 16 times greater
Grass appears green because
it reflects green light and absorbs other colors
The amount of gravitational potential energy released as an object falls depends on
its mass and the distance it falls, as well as the rate of gravitational acceleration.
The ultimate source of energy that powers the Sun is
mass energy of hydrogen fusing into helium.
Newton's second law of motion tells us that the net force applied to an object equals its
mass times acceleration.
Momentum is defined as
mass times velocity.
What quantities does angular momentum depend upon?
mass, velocity, and radius
The mass of Jupiter can be calculated by
measuring the orbital period and distance of one of Jupiter's moons.
Kepler's third law of planetary motion
more distant planets orbit the Sun at slower average speeds, obeying the precise mathematical relationship p2 =a3.
If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be:
one-quarter as strong.
Which of the following are allowed orbital paths under gravity?
parabolic, elliptical, hyperbolic These allowed orbital paths are explained by Newton's Laws of motion and gravitation.
The study of energy levels in atoms is called
quantum mechanics.
Which of the following is not a conserved quantity?
radiation
Thermal radiation is defined as
radiation that depends only on the emitting object's temperature.
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
radio
From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
radio, infrared, visible light, ultraviolet, X rays, gamma rays
Which of the following wavelength regions can be studied with telescopes on the ground?
radio, visible, and very limited portions of the infrared and ultraviolet regions
We can see each other in the classroom right now because we
reflect visible light.
Without telescopes or other aid, we can see the Moon because it
reflects visible light.
Which of the following studies is best suited to a time monitoring experiment?
studying whether a particular star's brightness is steady or variable
Tidal forces on Earth are causing
the Earth to slow down its rotation rate
What does angular resolution measure?
the angular size of the smallest features that the telescope can see
What does temperature measure?
the average kinetic energy of particles in a substance
The center of mass of a binary star system is
the balance point of the system, around which the two objects would revolve.
The wavelength of a wave is
the distance between two adjacent peaks of the wave.
Kepler's first law of planetary motion:
the orbit of each planet about the Sun is an ellipse with the Sun at one focus.
What is the purpose of adaptive optics?
to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
Any particular location on Earth experiences __________. one high tide and one low tide each day one high tide and one low tide each month two high tides and two low tides each month two high tides and two low tides each day two sets of high and low tides in the ocean, but only one set on land
two high tides and two low tides each day The video shows that any location on Earth passes through both tidal bulges and both tidal minima (the places where the tides are smallest) each day, which means two high tides and two low tides. Again, recall that this is true for both land and oceans, though tides are more noticeable in the oceans because water flows so much more readily than land.
Which of the following wavelength regions cannot be studied with telescopes on the ground?
ultraviolet X rays
Which of the following forms of light can be observed with telescopes at sea level? -X rays -ultraviolet light -visible light -infrared light -radio waves
visible light radio waves Both visible light and radio waves pass almost freely through Earth's atmosphere, and therefore are easily observed with ground-based telescopes. The only other light that can be observed with ground-based telescopes is infrared, but it can be detected only at high altitudes (such as mountaintops) and even then only in selected portions of the infrared spectrum.
In which of the following cases would you feel weightless?
while falling from a roof