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25 Cards in this Set
- Front
- Back
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If you have a 100-watt light bulb, how much energy does it use each minute? |
6,000 joules. |
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The frequency of a wave is |
all of the above. |
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How are wavelength, frequency, and energy related for photons of light? |
Longer wavelength means lower frequency and lower energy. |
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Which of the following statements about X rays and radio waves is not true? |
X rays travel through space faster than radio waves. |
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An electron-volt is |
an amount of energy much smaller than a joule. |
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If you heat a gas so that collisions are continually bumping electrons to higher energy levels, whenthe electrons fall back to lower energy levels the gas produces |
an emission line spectrum. |
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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. |
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When white light passes through a cool cloud of gas, we see |
an absorption line spectrum. |
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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. |
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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. |
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What is the difference between energy and power? |
Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time. |
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Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon? |
its wavelength and energy. |
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When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called_______. |
photons. |
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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 |
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Thermal radiation is defined as ________. |
radiation with a spectrum whose shape depends only on the temperature of the emitting object. |
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According to the laws of thermal radiation, hotter objects emit photons with ________. |
a shorter average wavelength. |
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Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you? |
The wavelengths of spectral lines in the star's spectrum. |
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The spectra of most galaxies show redshifts. This means that their spectral lines ________. |
have wavelengths that are longer than normal. |
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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? |
The star is moving toward us. |
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In what part of the spectrum would you need to be able to see so that you could detect the light emitted by students in astronomy class? |
infrared. |
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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. |
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If one object has a large redshift and another object has a small redshift, what can we concludeabout these two objects? |
The one with the large redshift is moving away from us faster than the one with the smallredshift. |
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Suppose you see two stars: a blue star and a red star. Which of the following can you concludeabout the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws ofthermal radiation.) |
The blue star has a hotter surface temperature than the red star. |
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You observe the same spectral line in two stars that are identical in every way except that onerotates faster than the other. How does the spectral line differ between the two? |
The line in the faster rotating star is broader. |
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If two objects are the same size but one object is 3 times hotter than the other object, the hotterobject emits |
81 times more energy. |
