AST1002 CHAPTER 5-13 WITH
COMPLETE SOLUTION
From shortest to longest wavelength, which of the following correctly orders
the different categories of electromagnetic radiation? - ANSWER gamma
rays, X rays, ultraviolet, visible light, infrared, radio
Which forms of light are lower in energy and frequency than the light that
our eyes can see? - ANSWER infrared and radio
When considering light as made up of individual "pieces," each characterized
by a particular amount of energy, the pieces are called _________. - ANSWER
photons
Suppose you know the frequency of a photon and the speed of light. What
else can you determine about the photon? - ANSWER its wavelength and
energy
Suppose you built a scale-model atom in which the nucleus is the size of a
tennis ball. About how far would the cloud of electrons extend? - ANSWER
Several kilometers
Which of the following best describes the fundamental difference between
two different chemical elements (such as oxygen and carbon)? - ANSWER
They have different numbers of protons in their nucleus.
Consider an atom of carbon in which the nucleus contains 6 protons and 7
neutrons. What is its atomic number and atomic mass number? - ANSWER
atomic number = 6; atomic mass number = 13
,If we say that a material is opaque to ultraviolet light, we mean that it
_________. - ANSWER absorbs ultraviolet light
Suppose you look at a detailed spectrum of visible light from some object.
How can you decide whether it is an emission line spectrum or an absorption
line spectrum? - ANSWER An emission line spectrum consists of bright lines
on a dark background, while an absorption line spectrum consists of dark
lines on a rainbow background.
An atom that has fewer electrons than protons is called a/an _________. -
ANSWER ion
Thermal radiation is defined as _________. - ANSWER radiation with a spectrum
whose shape depends only on the temperature of the emitting object
According to the laws of thermal radiation, hotter objects emit photons with
_________. - ANSWER a shorter average wavelength
Suppose you want to know the chemical composition of a distant star. Which
piece of information is most useful to you? - ANSWER the wavelengths of
spectral lines in the star's spectrum
The spectra of most galaxies show redshifts. This means that their spectral
lines _________. - ANSWER have wavelengths that are longer than normal
What does angular resolution measure? - ANSWER The angular size of the
smallest features that the telescope can see.
Which of the following statements best describes the two principle
advantages of telescopes over eyes? - ANSWER Telescopes can collect far
more light with far better angular resolution.
What is the purpose of interferometry? - ANSWER It allows two or more
,small telescopes to achieve the angular resolution of a much larger telescope.
What do astronomers mean by light pollution? - ANSWER Light pollution is
light from human sources that makes it difficult to see the stars at night.
The stars in our sky twinkle in brightness and color because of _________. -
ANSWER turbulence in the Earth's atmosphere
What is the purpose of adaptive optics? - ANSWER It reduces blurring caused
by atmospheric turbulence for telescopes on the ground.
What is the purpose of interferometry? - ANSWER It allows two or more
small telescopes to achieve the angular resolution of a much larger telescope.
Suppose you watch a leaf bobbing up and down as ripples pass it by in a
pond. You notice that it does two full up and down bobs each second. Which
statement is true of the ripples on the pond? - ANSWER They have a
frequency of 2 hertz.
Which of the following best describes why we say that light is an
electromagnetic wave? - ANSWER The passage of a light wave can cause
electrically charged particles to move up and down.
Each of the following describes an "Atom 1" and an "Atom 2." In which case
are the two atoms different isotopes of the same element? - ANSWER
nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2:
nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons
Which of the following statements is true of green grass? - ANSWER It
absorbs red light and reflects green light.
Which of the following conditions lead you to see an absorption line
spectrum from a cloud of gas in interstellar space? - ANSWER The cloud is
, cool and lies between you and a hot star.
Which of the following statements about thermal radiation is always true? -
ANSWER A hot object emits more radiation per unit surface area than a cool
object.
Betelgeuse is the bright red star representing the left shoulder of the
constellation Orion. All the following statements about Betelgeuse are true.
Which one can you infer from its red color? - ANSWER Its surface is cooler
than the surface of the Sun.
Laboratory measurements show hydrogen produces a spectral line at a
wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the
same hydrogen line at a wavelength of 486.0 nm. What can we conclude? -
ANSWER The star is moving toward us.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger
redshift than Star Y. What can you conclude? - ANSWER Star X is moving
away from us faster than Star Y.
TRUE or FALSE:
The total amount of light in the spectrum tells us the star's radius. - ANSWER
FALSE
We cannot measure radius from a spectrum without additional information.
The angular separation of two stars is 0.1 arcseconds and you photograph
them with a telescope that has an angular resolution of 1 arcsecond. What
will you see? - ANSWER The photo will seem to show only one star rather
than two.
How does the light-collecting area of an 8-meter telescope compare to that
COMPLETE SOLUTION
From shortest to longest wavelength, which of the following correctly orders
the different categories of electromagnetic radiation? - ANSWER gamma
rays, X rays, ultraviolet, visible light, infrared, radio
Which forms of light are lower in energy and frequency than the light that
our eyes can see? - ANSWER infrared and radio
When considering light as made up of individual "pieces," each characterized
by a particular amount of energy, the pieces are called _________. - ANSWER
photons
Suppose you know the frequency of a photon and the speed of light. What
else can you determine about the photon? - ANSWER its wavelength and
energy
Suppose you built a scale-model atom in which the nucleus is the size of a
tennis ball. About how far would the cloud of electrons extend? - ANSWER
Several kilometers
Which of the following best describes the fundamental difference between
two different chemical elements (such as oxygen and carbon)? - ANSWER
They have different numbers of protons in their nucleus.
Consider an atom of carbon in which the nucleus contains 6 protons and 7
neutrons. What is its atomic number and atomic mass number? - ANSWER
atomic number = 6; atomic mass number = 13
,If we say that a material is opaque to ultraviolet light, we mean that it
_________. - ANSWER absorbs ultraviolet light
Suppose you look at a detailed spectrum of visible light from some object.
How can you decide whether it is an emission line spectrum or an absorption
line spectrum? - ANSWER An emission line spectrum consists of bright lines
on a dark background, while an absorption line spectrum consists of dark
lines on a rainbow background.
An atom that has fewer electrons than protons is called a/an _________. -
ANSWER ion
Thermal radiation is defined as _________. - ANSWER radiation with a spectrum
whose shape depends only on the temperature of the emitting object
According to the laws of thermal radiation, hotter objects emit photons with
_________. - ANSWER a shorter average wavelength
Suppose you want to know the chemical composition of a distant star. Which
piece of information is most useful to you? - ANSWER the wavelengths of
spectral lines in the star's spectrum
The spectra of most galaxies show redshifts. This means that their spectral
lines _________. - ANSWER have wavelengths that are longer than normal
What does angular resolution measure? - ANSWER The angular size of the
smallest features that the telescope can see.
Which of the following statements best describes the two principle
advantages of telescopes over eyes? - ANSWER Telescopes can collect far
more light with far better angular resolution.
What is the purpose of interferometry? - ANSWER It allows two or more
,small telescopes to achieve the angular resolution of a much larger telescope.
What do astronomers mean by light pollution? - ANSWER Light pollution is
light from human sources that makes it difficult to see the stars at night.
The stars in our sky twinkle in brightness and color because of _________. -
ANSWER turbulence in the Earth's atmosphere
What is the purpose of adaptive optics? - ANSWER It reduces blurring caused
by atmospheric turbulence for telescopes on the ground.
What is the purpose of interferometry? - ANSWER It allows two or more
small telescopes to achieve the angular resolution of a much larger telescope.
Suppose you watch a leaf bobbing up and down as ripples pass it by in a
pond. You notice that it does two full up and down bobs each second. Which
statement is true of the ripples on the pond? - ANSWER They have a
frequency of 2 hertz.
Which of the following best describes why we say that light is an
electromagnetic wave? - ANSWER The passage of a light wave can cause
electrically charged particles to move up and down.
Each of the following describes an "Atom 1" and an "Atom 2." In which case
are the two atoms different isotopes of the same element? - ANSWER
nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2:
nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons
Which of the following statements is true of green grass? - ANSWER It
absorbs red light and reflects green light.
Which of the following conditions lead you to see an absorption line
spectrum from a cloud of gas in interstellar space? - ANSWER The cloud is
, cool and lies between you and a hot star.
Which of the following statements about thermal radiation is always true? -
ANSWER A hot object emits more radiation per unit surface area than a cool
object.
Betelgeuse is the bright red star representing the left shoulder of the
constellation Orion. All the following statements about Betelgeuse are true.
Which one can you infer from its red color? - ANSWER Its surface is cooler
than the surface of the Sun.
Laboratory measurements show hydrogen produces a spectral line at a
wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the
same hydrogen line at a wavelength of 486.0 nm. What can we conclude? -
ANSWER The star is moving toward us.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger
redshift than Star Y. What can you conclude? - ANSWER Star X is moving
away from us faster than Star Y.
TRUE or FALSE:
The total amount of light in the spectrum tells us the star's radius. - ANSWER
FALSE
We cannot measure radius from a spectrum without additional information.
The angular separation of two stars is 0.1 arcseconds and you photograph
them with a telescope that has an angular resolution of 1 arcsecond. What
will you see? - ANSWER The photo will seem to show only one star rather
than two.
How does the light-collecting area of an 8-meter telescope compare to that
