A radio telescope - StudentOfFortune.com

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luckylu
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$1.00 A radio telescope

From Physics: Astrophysics
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Due on Feb. 11, 2009
Asked on Feb 11, 2009 at 3:57:11PM

Q:
A radio telescope with a 50m diameter dish receives a radio signal of power 4.0x10^-13W from a radio source at a distance of 700 kiloparsecs. Calculate the total power emitted by the radio source within the range of frequencies which the telescope receives, assuming that the radio source radiates uniformly in all directions.

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stevesov
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$1.00 Mostly geometry.

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Posted on Feb 11, 2009 at 8:08:38PM

A:
Preview: ... this point source and you find that it measures 4.0 * 10^-13 watts at the distance in question. To figure out the total power output of the point source, you need to look at the ratio of your measurement area to the total area. Your measurement area is a 50m diameter circle, the area of a circle is pi * r^2, so get your radius (half the diameter) and that tells you the measured area is pi * 25^2, or 625 pi m^2. Your sphere is a big one. According to NASA, a "parsec" i ...

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