3 - Optics & Telescope

3 - Optics & Telescope - Optics Telescopes Today...

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Today : basics Wed : high tech. modern Digital Universe http://www.haydenplanetrium.org/universe/
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Faintest objects : ~ 10 -16 W/m 2 like 100 W bulb at 10 6 km distant astronomical objects faint due to 1/r 2 law assuming no absorption : total energy through spherical surfaces per sec = const. L = 4 π R 2 Brightness
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Telescopes collect light from faint stars, etc. must bend light paths (refraction and reFection) sensitivity = telescope area = p R 2 (R=radius of reFector) (also depends on detectors) resolution better, the bigger the telescope but … for opt. tel. atmospheric ‘seeing’ limits resolution to 0.5 arcsec (can use ‘adaptive optics to correct ‘seeing or space)
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2 physical mechanisms : refraction : bending at the interface between a dense medium and a less dense medium reFection (at an electrically conductive interface) q 1 q 2 q 1 = q 2 Silvered glass dense (water, glass) n 2 =c/c 2 less dense (air, vacume) n 1 =c/c 1 q 1 q 2 Snell's Law : n 1 sinq 1 =n 2 sinq 2
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Fermat’s principle : light travels the path taking least time (actually the ‘stationary’ path max. constructive interference) AEB = AEB’ minimum s.t. E C i.e straight line path
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3 - Optics & Telescope - Optics Telescopes Today...

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