Chapter5 Review
Refracting telescopes use a lens to gather light to form an image
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Problems with Refracting Telescope
Hard to make a large lens free of defects because light will travel through the lens
Only the edges are support, so the middle sags
Glass is opaque to certain freq of light
Chromatic aberration - different colors of light come to focus at different focal lengths
Reflecting telescopes use a mirror to reflect light to form an image
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Benefits of Reflecting Telescopes
Defects in the glass are fine, as long as the surface of the mirror is free from defects
No chromatic aberration
Mirrors are supported by a backup structure
See Reflecting telescope designs to see the light path
Properties of Telescopes
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Magnification - ratio of the size of an object when seen through a telescope to its size
when seen with the unaided eye
Light Gathering Power - the amount of light a telescope can collect
Resolution - Smallest angular separation detectable with an instrument
Radio Telescopes
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Radio telescopes need to be big
Cosmic Radio sources are very weak, so need a large collecting area
Radio wavelengths are large
Need large dish to improve the resolution
Effects of the Atmosphere
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Turbulent air flow in Earth's atmosphere distorts our view, causing stars to appear to
twinkle
Radio and Visible light pass easily through Earth's atmosphere
Telescopes at high altitudes can observe Gamma ray, X ray, UV , IR