Astronomy Ch 3.7 – Flashcards
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When multiple radio telescopes are used for interferometry, resolving power is most improved by increasing
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the distance between telescopes.
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If you throw a rock into a pond, it creates a wave in the water. What is responsible for creating an electromagnetic wave?
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A vibrating charged particle
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What property of a telescope influences its resolving power?
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The size of the main mirror or lens
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What observations at wavelengths other than optical or radio?
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Most observations at wavelengths other than optical or radio need to be conducted by space-based telescopes.
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What is meant in astronomy by the phrase "active optics"?
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Rapid modifications are made to the tilt and location of the elements of a telescope to correct for the effects of atmospheric and instrumental distortion.
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What type of electromagnetic waves has the shortest wavelength?
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X-ray
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What is a fact about the use of infrared telescopes?
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The detector and telescope must be cooled to very low temperatures.
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What is the primary advantage of techniques of radio interferometry?
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An increase in resolving power
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If we double the diameter of a telescope's mirror, what happens to its light-gathering ability?
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Light-gathering ability quadruples.
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The energy of a photon is inversely proportional to the wavelength of the radiation. T or F
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True
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What is a fact about the Spitzer Space Telescope?
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It orbits the Sun a little behind Earth.
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Electromagnetic (EM) radiation penetrates the atmosphere of Earth at what portions of the electromagnetic spectrum?
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In visible, some IR, and some radio wavelengths
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Radio telescopes would NOT represent a good choice for astronomical study of ________.
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ordinary stars
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The number of waves that pass a point each second measures ________.
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frequency
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What would you need to obtain a successful X-ray image of a high-energy source?
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A telescope designed and built to be launched into space. A cosmic source of high temperature.
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The best way to study young stars hidden behind interstellar dust clouds would be to use
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infrared light.
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What fraction of the entire electromagnetic spectrum is spanned by visible light?
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Visible light covers a tiny fraction of the electromagnetic spectrum.
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Radio telescopes are large in part to improve their angular resolution, which is poor because of the long wavelengths at which they are used to observe the skies. T or F
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True
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Which of the following is an advantage the Hubble Space Telescope has over ground-based telescopes?
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There is no blurring due to the atmosphere.
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What is the main reason that ultraviolet astronomy must be done in space?
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Earth's atmosphere absorbs most ultraviolet wavelengths.
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Gamma-ray telescopes employ the same basic design that optical instruments use. T or False
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False
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The term seeing is used to describe how faint an object can be detected by a telescope. T or F
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False
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As telescopes become larger and larger, astronomers favor ________.
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reflecting telescopes, in part because large lenses and mirrors sag under their own weight, and it is easier to support a mirror along its entire back side than it is to support a lens only around its edge
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For a wave of constant velocity, such as an electromagnetic wave, how are the wavelength and frequency related?
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Wavelength is inversely proportional to the frequency.
