- Grossmont-Cuyamaca Community College District
- Astronomy 110
- Chapter 3
Last Modified: 2014-02-17
What is the relationship between color and wavelength for light?
Our present understanding of the nature of light is that it
Between infrared and ultraviolet
Which of the following wave effects is NOT electromagnetic in nature?
The two ranges of electromagnetic radiation for which the Earth's atmosphere is reasonably transparent are
visible and radio radiation.
The main reason for building large optical telescopes on the Earth's surface is
to collect more light from faint objects.
What is refraction of light?
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
A Newtonian telescope uses
one curved mirror and one flat mirror at a 45∞ angle to the first mirror axis.
concave primary mirror followed by a smaller convex secondary mirror that reflects light back through a hole in the primary mirror.
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?
In general, doubling the diameter of an optical telescope will
quadruple the light-gathering power and double the angular resolution.
What is a CCD (charge-coupled device)?
An array of small light-sensitive elements that can be used in place of photographic film to obtain and store a picture
The speed of light in glass is slower than the speed of light in a vacuum.
What is the main optical element of a refracting telescope?
All wavelengths of light are reflected by the same amount irrespective of color.
A refracting telescope
A spherical mirror suffers from spherical aberration because
different parts of the mirror focus the light at different distances from the mirror.
The major cause of blurring and unsharp images of objects observed through very large telescopes, at the extreme limit of magnification, is
air turbulence in the Earth's atmosphere.
The best Earth-based sites for modern large astronomical telescopes, which provide the least seeing effects upon astronomical images, are
on the tops of high mountains, above a large fraction of the disturbing atmosphere.
Why was adaptive optics developed?
To compensate for image distortion caused by the Earth's atmosphere
How does angular resolution for a given diameter of telescope depend on wavelength?
Angular resolution worsens as wavelength increases.
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
angular resolution gets worse as wavelength increases.
How is interferometry used in radio astronomy?
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.
Telescopes are placed in space to view distant galaxies primarily
to avoid the absorption and distortion of the light or other radiations within the atmosphere of the Earth.
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