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  1. Reflection
    The incident light traveling at an angle (i) reflects off a surface at the same angle (r) between the reflected ray and the perpendicular (p).
  2. Refraction
    The change in the direction of light as it passes through a medium.  Light slows as it passes through a denser medium than a vacuum.
  3. Lens
    Glass that is shaped to make distant objects closer and brighter.
  4. Mirror
    Glass that is coated with silver, aluminum, or a similar highly reflective substance that reflects light waves.
  5. Spectroscopy
    Measures the spectra of an object, not recording an image of an object.  A diffraction grating is used to break up light into a spectrum.
  6. Hubble Space Telescope
    A telescope that orbits the earth at 600km.  It can measure any wavelength of light from 115 nm to 1 micro n.
  7. Atmospheric Distortion
    The bending of light by the earth’s atmosphere.
  8. Prime Focus
    An observer or instrument is placed directly at the focal point, within the barrel of a telescope.  Used only in large reflecting telescopes.
  9. Cassegrain Focus
    Has a convenient, accessible focal point in a telescope.  A hole is drilled directly through the center of the primary mirror, and a convex secondary mirror placed in front of the original focal point reflects the light rays back through the hole.
  10. Angular Resolution
    A quantity that gauges how well fine details of objects can be seen.  It is the angle between 2 stars.  The smaller the angle, the sharper the resolution.
  11. Adaptive Optics
    A system that compensates for atmospheric turbulence, so that the angular resolution can be smaller than the size of the seeing disk.  As turbulence causes a star to “dance” around, sensors detect the “dancing” and adjust the mirror accordingly.
  12. Secondary Mirror
    A convex mirror that is placed in front of the original focal point in a reflecting telescope.  It reflects light rays from the primary mirror to an observer, instrument, or another mirror.
  13. Interferometry
    A technique designed to improve angular resolution.  The idea is to have 2 widely separated telescopes observe the same object at the same time, then use fiber optic cables to pipe the light signals to a central location, where they are combined to form a single image.
  14. Photometry
    The measurement of the brightness of stars and other astronomical objects.
  15. Newtonian Reflector
    A reflecting telescope that has a flat mirror at a 45 degree angle in front of the focal point in the barrel of a telescope.  This secondary mirror reflects the light rays to one side of the barrel, where an eyepiece lens is placed to magnify the image.
  16. Light Gathering Power
    The light-gathering power of a telescope is directly proportional to the objective lens, which is proportional the square of the lens diameter.
  17. Primary Mirror
    A concave mirror that that reflects light rays to a focal point.

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2012-10-28 05:41:23

Chapter 5 6 16 17
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