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Refracting
Telescopes
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Refraction--how lenses
and prisms work
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light slows down when
it goes through matter
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why your arm looks bent in
a swimming pool
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how magnifying glasses work
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A curved piece of glass forms
a lens
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focus of lens is where
rays of light meet
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an extended object forms
an image at the focal plane
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a focal plane works for projection
onto film but not for your eye
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refracting telescopes need
at least two lenses, objective and eyepiece
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spacing between lenses has
to be just right (why you need a focus adjustment)
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Magnification
= FL(obj) / FL(eye)
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telescope gathers more light
than your eye
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Eye pupil = 0.5 cm diameter
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Galileo's telescope = 3 cm
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refracting telescope on roof
= 15 cm
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Washburn observatory = 38
cm
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Lick (CA) = 91 cm
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Yerkes (Lake Geneva WI) =
101 cm
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Collecting area = p(d/2)2
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eye = 0.2 cm2
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Yerkes = 8000 cm2
Refraction
analogy
Refraction
diagram
Image
diagram
Refracting
telescope schematic
Yerkes
telescope and Lens
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