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Astronomy 101 final exam > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

Which of the following best describes why the Sun’s spectrum contains black lines over an underlying rainbow?

A

The Sun’s hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.

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2
Q

Suppose we want to know what the Sun is made of. What should we do?

A

Compare the wavelengths of lines in the Sun’s spectrum to the wavelengths of lines produced by chemical elements in the laboratory.

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3
Q

Which of the following best describes why we say that light is an electromagnetic wave?

A

The passage of a light wave can cause electrically charged particles to move up and down.

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4
Q

Which of the following statements about X rays and radio waves is not true?

 X rays have higher frequency than radio waves.
 X rays and radio waves are both forms of light, or electromagnetic radiation.
 X rays travel through space faster than radio waves.
 X rays have shorter wavelengths than radio waves.
A

X rays travel through space faster than radio waves

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5
Q

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?

A

several kilometers

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6
Q

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?

 Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons; Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons
 Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons; Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons
 Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons
 Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons; Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons
A

Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons

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7
Q

Which of the following statements is true of green grass?
It transmits all colors of light except green.
It means the lawn is healthy.
It absorbs red light and reflects green light.
It absorbs red light and emits green light.

A

It absorbs red light and reflects green light.

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8
Q

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

A

The cloud is cool and lies between you and a hot star.

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9
Q

Which of the following statements about thermal radiation is always true?

A

A hot object emits more radiation per unit surface area than a cool object.

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10
Q

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?

A

Its surface is cooler than the surface of the Sun.

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11
Q

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?

A

the star is moving towards us

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12
Q

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

A

Star X is moving away from us faster than Star Y.

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13
Q

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?

A

The total amount of light in the spectrum tells us the star’s radius.

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14
Q

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?

A

The photo will seem to show only one star rather than two.

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15
Q

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?

A

The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

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16
Q

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

A

It is closer to the stars.

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17
Q

The Chandra X-ray Observatory must operate in space because:

A

X rays do not penetrate the Earth’s atmosphere

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18
Q

Which of the following is always true about images captured with X-ray telescopes?

A

They are always shown with colors that are not the true colors of the objects that were photographed.

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19
Q

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

A

gamma rays, X rays, ultraviolet, visible light, infrared, radio

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20
Q

Which forms of light are lower in energy and frequency than the light that our eyes can see?

A

infrared and radio

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21
Q

When considering light as made up of individual “pieces,” each characterized by a particular amount of energy, the pieces are called _________.

A

photons

22
Q

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?

A

They have a frequency of 2 hertz.

23
Q

Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?

A

its wavelength and energy

24
Q

Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?

A

They have different numbers of protons in their nucleus.

25
Q

Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?

A

atomic number = 6; atomic mass number = 13

26
Q

If we say that a material is opaque to ultraviolet light, we mean that it _________.

A

absorbs ultraviolet light

27
Q

Visible light from a distant star can be spread into a spectrum by using a glass prism or ______.

A

a diffraction grating

28
Q

Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?

A

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.

29
Q

An atom that has fewer electrons than protons is called a/an _________.

A

ion

30
Q

Thermal radiation is defined as _________.

A

radiation with a spectrum whose shape depends only on the temperature of the emitting object

31
Q

According to the laws of thermal radiation, hotter objects emit photons with _________.

A

a shorter average wavelength

32
Q

Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

A

the wavelengths of spectral lines in the star’s spectrum

33
Q

The spectra of most galaxies show redshifts. This means that their spectral lines _________.

A

have wavelengths that are longer than normal

34
Q

What is the angular resolution of the human eye?

A

about 1 arcminute, or 1/60 of a degree

35
Q

Which of the following statements best describes the two principle advantages of telescopes over eyes?

A

Telescopes can collect far more light with far better angular resolution.

36
Q

What do astronomers mean by light pollution?

A

Light pollution is light from human sources that makes it difficult to see the stars at night.

37
Q

The stars in our sky twinkle in brightness and color because of _________.

A

turbulence in the Earth’s atmosphere

38
Q

What is the purpose of adaptive optics?

A

It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

39
Q

What is the purpose of interferometry?

A

It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.

40
Q

Which of the following best describes why we say that light is an electromagnetic wave?

A

The passage of a light wave can cause electrically charged particles to move up and down

41
Q

Which of the following statements about X rays and radio waves is not true?
X rays travel through space faster than radio waves.
X rays have higher frequency than radio waves.
X rays have shorter wavelengths than radio waves.
X rays and radio waves are both forms of light, or electromagnetic radiation.

A

X rays travel through space faster than radio waves.

42
Q

The largest effective telescope, created by radio interferometry, is the size of

A

Earth

43
Q

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?

A

radio

44
Q

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

A

the planet is rotating

45
Q

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.)

A

the blue star has a hotter surface temperature than the red star

46
Q

When an electron in an atom goes from a higher energy state to a lower energy state, the atom

A

emits a photon of a specific frequency

47
Q

Spectra from neutral atoms compared with spectra from ionized atoms of the same element

A

have different sets of spectral lines

48
Q

If a material is transparent, then it

A

transmits light well

49
Q

Everything looks red through a red filter because

A

the filter transmits red light and absorbs other colors.

50
Q

An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

A

26 protons, 30 neutrons, 26 electrons

51
Q

Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number?

A

The atomic number is 79, and the atomic mass number is 197.

52
Q

The frequency of a wave is

A

the number of peaks passing by any point each second.
equal to the speed of the wave divided by the wavelength of the wave.
measured in hertz (Hz).
measured in cycles per second.

Astronomy 101 final exam (13 decks)

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