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27 Cards in this Set
- Front
- Back
What is light?
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Light, more properly "visible light", is one form of electromagnetic radiation. All electromagnetic radiation (radio waves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays) has both wave and particle properties.
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What type of electromagnetic radiation is most dangerous to life?
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Gamma rays are most dangerous
UV light from sun is the most common though. |
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What is the main purpose of a telescope?
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A telescope is designed primarily to collect as much light as possible.
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Why do stars twinkle?
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Rapid changes in density of the Earth's atmosphere cause passing starlight to change direction, making stars appear to twinkle.
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What type(s) of electromagnetic radiation can telescopes currently detect?
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Telescopes have been built tat can observe the entire electromagnetic spectrum.
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______, compact units of vibrating electric and magnetic fields, all carry energy through space at the same speed, "the speed of light" (300,000 km/s in a vaccuum, slower in any medium).
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Photons
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Radio waves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays are the forms of ____________ __________. They travel as photons, sometimes behaving as particles, sometimes as waves.
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electromagnetic radiation
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________ light occupies only a small portion of the electromagnetic spectrum.
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Visible
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The wavelength of a visible light photon is associated with its _______. Wavelengths of visible light range from about 400 nm for _______ light to 700 nm for _______ light.
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color
violet red |
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Infrared radiation and radio waves have wavelengths ______ than those of visible light. UV light, X rays, and gamma rays have wavelengths that are _______.
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longer
shorter |
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The motion of an object toward or away from an observer causes the observer to see all the colors from the object to __________ or _________, respectively. This is generically called _________ shift.
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redshift
blueshift doppler |
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A telescope's most important function is to gather as much _______ as possible. Its second function is to reveal the observed object in as much detail as possible. Often the least important function of a telescope is to ________ objects.
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light
magnify |
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_________ telescopes, or __________, produce images by reflecting light rays from concave mirrors to a focal point or focal plane.
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reflecting
reflectors |
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_________ telescopes, or __________, produce images by benging light rays as they pass through glass lenses. Glass impurity, opacity to certain wavelengths, and structural difficulties make inadvisable to build extremely large refractors. __________ are not subject to many of the problems that limit the usefullness of refractors.
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Refracting
refractors reflectors |
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What are used to record images?
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Charged-coupled devices (CCD's)
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__________ telescopes are being built with active and adaptive optics. These advanced technologies yield resolving power comparable to the Hubble Space Telescope.
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Earth-based
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________ telescopes have large reflecting antennas (dishes) that are used to focus radio waves.
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Radio
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Very sharp radio images are produces with arrays of radio telescopes linked together in a technique called ____________.
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interferometry
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The Earth's atmosphere is fairly transparent to most visible light and radio waves, along with some infrared and UV radiation, arriving from space, but it absorbs much of the _______________ __________ at other wavelengths.
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electromagnetic radiation
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Explain some of the advantages of relecting telescopes over refracting telescopes.
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Refracting:
1. glass impurity 2. opacity to certain wavelengths 3. structural difficulties 4. can't build big ones reflectors: 1. don't have those problems |
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What are the three major function of the telescope?
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1. (most important) to gather as much light as possible.
2. reveal the observed object in as much detail as possible. 3. (least important) to magnify objects |
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T or F
An light wave always has to travel through a medium. |
True
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Do we consider, for astronomy, a photon to be a wave or particle?
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wave
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What is angular resolution?
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It measures the clarity of the image
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Why must astronomers use satellites and Earth-orbiting observatories to study the heavens at X-ray wavelengths?
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Because they don't penetrate through the Earth's atmosphere because of the different gases in atmosphere.
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What are NASA's 4 great observatories and in what parts of the electromagnetic spectrum do they observe?
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Hubble Space Telescope -observes the Universe at ultraviolet, visual, and near-infrared wavelengths
Compton Gamma Ray Observatory - gamma ray Chandra X-ray Observatory - X-ray Spitzer Space Telescope - thermal infrared rays |
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Why did Romer's observations of the eclipses of Jupiter's moons support of the heliocentric, but not the geocentric, cosmology?
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because when Jupiter and the Earth are in opposition, when they are on the same side as the sun, The Earth-Jupiter distance is relatively short compared to when Jupiter is near conjunction.
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