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1 | | How do astronomers calculate a telescope's light collecting area (A)?
(where r = radius of the telescopes mirror or lens, and B is "pi" or 3.14159) |
| | A) | A = 2Br |
| | B) | A = Br2 |
| | C) | A = 4Br2 |
| | D) | A = 4/3 Br3 |
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2 | | Telescope A has a mirror twice the diameter of telescope B’s mirror. How does A's light-gathering power compare to B's? |
| | A) | A gathers 1/2 the light that B does. |
| | B) | A gathers twice the light that B does. |
| | C) | A gathers 4 times the light that B does. |
| | D) | A gathers 1/4th as much light as B does. |
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3 | | A telescope's resolving power measures its ability to see |
| | A) | fainter sources. |
| | B) | more distant sources. |
| | C) | finer details in sources. |
| | D) | larger sources. |
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4 | | One way to increase the resolving power of a telescope is to |
| | A) | make its mirror bigger. |
| | B) | make its mirror smaller. |
| | C) | replace its mirror with a lens of the same diameter. |
| | D) | observe objects using longer wavelengths. |
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5 | | What causes the image of a star to “twinkle” or scintillate? |
| | A) | irregularities in the density of layers of Earth’s atmosphere, rapidly refracting the light. |
| | B) | the flickering fusion process in the stars. |
| | C) | a purely physiological reaction in the eye. |
| | D) | none of these answers are correct. |
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6 | | What process limits a telescope's resolving power? |
| | A) | Reflection |
| | B) | Refraction |
| | C) | Diffraction |
| | D) | Distraction |
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7 | | What is the difference between a reflecting and a refracting telescope? |
| | A) | A reflecting telescope uses a lens to focus light; a refracting telescope uses a mirror. |
| | B) | A reflecting telescope uses a mirror to focus light; a refracting telescope uses a lens. |
| | C) | Both use a mirror to focus light, but a reflecting telescope uses mirrors elsewhere to bend light. |
| | D) | There is no difference. "Refracting" is an outmoded way of saying "reflecting." |
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8 | | Light travels __ in water than in air |
| | A) | faster |
| | B) | slower |
| | C) | at the same speed |
| | D) | perpendicular to |
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9 | | Which of the these is a reason for using mirrors rather than lenses in telescopes? |
| | A) | Lenses are more expensive to make than mirrors. |
| | B) | Most transparent materials focus light of different colors to different spots. |
| | C) | Lenses can only be supported by their edges, making them sag in the middle (mirrors can be supported from behind). |
| | D) | All of the above. |
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10 | | Why use an interferometer? |
| | A) | Its two widely-spaced mirrors act like one giant telescope with increased collecting area. |
| | B) | Its two widely-spaced mirrors act like one giant telescope with increased resolving power. |
| | C) | By putting one mirror above the other you can make the instrument much smaller. |
| | D) | It can detect light at wavelengths not available to single telescopes. |
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11 | | Which of the following astronomical objects emit radiation mostly at non-visible wavelengths? |
| | A) | dust clouds in space |
| | B) | hot gas surrounding black holes |
| | C) | cold interstellar gas clouds |
| | D) | all of the above |
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12 | | Do astronomers use ground-based X-ray telescopes? |
| | A) | Yes, because they can penetrate gas clouds. |
| | B) | No, because no astronomical objects emit x-rays. |
| | C) | No, because x-rays cannot get through the Earth's atmosphere. |
| | D) | No, because astronomers have not yet devised detectors for x-rays. |
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13 | | Why does the useful resolving power of a ground-based telescope not match it's theoretical value? |
| | A) | Mirrors can't be built accurately enough. |
| | B) | The atmosphere blurs the image, decreasing the resolving power. |
| | C) | Mirrors cannot collect enough light to reach their theoretical expectations. |
| | D) | The theoretical value can only be reached when there is a Full Moon. |
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14 | | On some telescopes, actuators on the mirror change its shape to match distortions in the atmosphere. What is this technique called? |
| | A) | Actuary observing |
| | B) | Interferometry. |
| | C) | Refraction |
| | D) | Adaptive Optics |
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15 | | Which of the following is a reason to build an observatory in space? |
| | A) | They are much less expensive than ground-based observatories. |
| | B) | They can last forever. |
| | C) | To avoid atmospheric blurring. |
| | D) | There is no good reason to build a space-based observatory. |
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