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17 Cards in this Set
- Front
- Back
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Which of the following statements about light focusing is not true? Film should be placed at the focal plane in a camera. In a healthy eye, light is focused on the retina. The focal plane of a reflecting telescope is always located within a few inches of the primary mirror. If you try to look at an image that is not formed at the focal plane, it will be blurry. Light can be focused with a lens or a mirror. |
The focal plane of a reflecting telescope is always located within a few inches of the primary mirror. |
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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. You will not be able to see these two stars at all. The two stars will appear to be touching, looking rather like a small dumbbell. You will see only the larger of the two stars, not the smaller one. You will see two distinct stars. |
The two stars will look like a single point of light. |
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Which of the following is a principal advantage of CCDs over photographic film? CCDs can be attached to modern telescopes more easily than cameras. CCDs allow long exposures (e.g., minutes or hours), and film does not. CCDs capture a much higher percentage of the incoming photons than does film. Images recorded with CCDs never require any image processing, while images recorded by film often do. CCDs can record the colors of astronomical objects accurately, while film cannot |
CCDs capture a much higher percentage of the incoming photons than does film. |
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Which of the following statements best describes the two principal advantages of telescopes over eyes? Telescopes have much more magnification and better angular resolution Telescopes can see farther without image distortion and can record more accurate colors. Telescopes can collect far more light with far better angular resolution. Telescopes can collect far more light with far greater magnification. Telescopes collect more light and are unaffected by twinkling. |
Telescopes can collect far more light with far better angular resolution. |
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What do we mean by the diffraction limit of a telescope? It describes the maximum exposure time for images captured with the telescope. It is the maximum size to which any telescope can be built. It describes the farthest distance to which the telescope can see. It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion. |
It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion. |
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Currently, the largest optical telescope mirrors have a diameter of 10 m 2 m 1 m 5 m |
10 m |
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Which of the following could not be determined by an observation that uses only spectroscopy? the speed at which a distant galaxy is moving away from us the size of a distant galaxy the chemical composition of a distant star the surface temperature of a distant star the rotation rate of a distant star |
the size of a distant galaxy |
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What is meant by spectral resolution? It is a measure of how close two point sources can be distinguished. It is the same as angular resolution when applied to telescopes operating at different wavelengths. It is a measure of how close two spectral lines can be distinguished. It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum. |
It is a measure of how close two spectral lines can be distinguished. |
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The largest effective telescope, created by radio interferometry, is the size of several football fields, in a natural depression in Puerto Rico. tens of miles across, in the deserts of New Mexico. Earth. the state of New Mexico. the continental United States |
Earth. |
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What does the technique of interferometry allow? It allows astronomers to make astronomical observations without interference from light pollution. It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes. It allows the same telescope to make images with both radio waves and visible light. It allows two or more telescopes to obtain a total light-collecting area much larger than the total light-collecting area of the individual telescopes. It allows us to determine the chemical composition of stars. |
It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes. |
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In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? radio X-ray infrared visible ultraviolet |
radio |
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Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? Observers on the ground can use it at any time of day (i.e., not only during their night). Stars do not twinkle when observed from space. It never has to close because of bad weather. It is closer to the stars It can observe infrared and ultraviolet light, as well as visible light. |
It is closer to the stars |
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Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? Astronomers and engineers enjoy the challenge of making new telescope designs. Photons of different energy behave differently and require different collection strategies. Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths. New telescopes incorporate new technology to increase their efficiency. Light pollution is worse at radio wavelengths than visible wavelengths. |
Photons of different energy behave differently and require different collection strategies. |
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Which of the following is not a good reason to place observatories on remote mountain tops? to reduce light pollution to be able to observe at radio wavelengths to reduce light distortion to be able to observe at infrared wavelengths to reduce light absorption |
to be able to observe at radio wavelengths |
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What is an artificial star? a satellite orbiting Earth the unseen member of a binary star system a possible source of dark matter in the universe a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations a meteor |
a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations |
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What do astronomers mean by light pollution? Light pollution refers to pollution caused by light industry as opposed to heavy industry. Light pollution refers to harmful gases emitted by common street lights. Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime. Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness. Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. |
Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. |
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Which of the following is always true about images captured with X-ray telescopes? They are always very pretty. They are always displayed in false color. They are always useful for seeing through things. They are always displayed with the highest possible angular resolution They are always displayed with north pointing upward in the images. |
They are always displayed in false color. |
