Chapter 3 Quiz Test Questions – Flashcards
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Electromagnetic radiation moving through space with the speed of light consists of
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C) Oscillating electric and magnetic fields, always inseparable, always having the same frequency and wavelength, and traveling in the same direction.
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What is the relationship between color and wavelength for light?
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C) Wavelength increases from violet to red.
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In which of the following parameters does a photon of blue light NOT differ from a photon of yellow light, in a vacuum?
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D) Speed
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What is the one fundamental difference between X rays and radio waves?
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B) Their wavelengths are very different.
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Our present understanding of the nature of light is that it
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C) displays behavior of both waves and particles.
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Visible light occupies what position in the whole electromagnetic spectrum?
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B) Between infrared and ultraviolet
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Which of the following wave effects is NOT electromagnetic in nature?
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B) Seismic waves
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The two ranges of electromagnetic radiation for which the Earth's atmosphere is reasonably transparent are
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B) visible and radio radiation.
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The main reason for building large optical telescopes on the Earth's surface is
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B) to collect more light from faint objects.
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What is refraction of light?
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D) The change in direction of a light ray as it passes at an angle from one transparent material to another which has a different optical density
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A Newtonian telescope uses
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B) one curved mirror and one flat mirror at a 45° angle to the first mirror axis.
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A Cassegrain reflecting telescope is constructed using a
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A) concave primary mirror followed by a smaller convex secondary mirror that reflects light back through a hole in the primary mirror.
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What is the magnification of a Newtonian telescope that has a primary mirror of diameter 0.25 m and focal length of 2 m when used with an eyepiece of focal length 25 mm and an optical diameter of 5 mm?
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C) 80 times
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In general, doubling the diameter of an optical telescope will
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A) quadruple the light-gathering power and double the angular resolution.
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What is a CCD (charge-coupled device)?
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D) An array of small light-sensitive elements that can be used in place of photographic film to obtain and store a picture
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How does the speed of light in a substance such as glass compare to the speed of light in a vacuum?
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C) The speed of light in glass is slower than the speed of light in a vacuum.
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What is the main optical element of a refracting telescope?
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D) A lens
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A refracting telescope has an objective lens of focal length 40 cm and a diameter of 10 cm, and an eyepiece of focal length 5 cm and diameter 1 cm. What is the magnifying power of this telescope?
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D) 8×
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What is the reason for the fact that a reflecting telescope used at prime focus does NOT suffer from chromatic aberration?
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C) All wavelengths of light are reflected by the same amount irrespective of color
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Which of the following types of telescopes is most seriously affected by chromatic aberration?
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B) A refracting telescope
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A spherical mirror suffers from spherical aberration because
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D) different parts of the mirror focus the light at different distances from the mirror.
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The major cause of blurring and unsharp images of objects observed through very large telescopes, at the extreme limit of magnification, is
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D) air turbulence in the Earth's atmosphere.
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The best Earth-based sites for modern large astronomical telescopes, which provide the least seeing effects upon astronomical images, are
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D) on the tops of high mountains, above a large fraction of the disturbing atmosphere.
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Why was adaptive optics developed?
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B) To compensate for image distortion caused by the Earth's atmosphere
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How does angular resolution for a given diameter of telescope depend on wavelength?
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A) Angular resolution worsens as wavelength increases.
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The main reason that the angular resolution of a 20-m diameter radio telescope is worse than that of a 0.5-m diameter optical telescope is that
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B) angular resolution gets worse as wavelength increases.
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How is interferometry used in radio astronomy?
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C) Signals from two or more different radio telescopes are combined to produce a single image of greater angular resolution than from any one telescope alone.
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Telescopes are placed in space to view distant galaxies primarily
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B) to avoid the absorption and distortion of the light or other radiations within the atmosphere of the Earth.
