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A spy satellite orbits at 250km above the Earth carrying 2.5 meters optical lens

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A spy satellite orbits at 250km above the Earth carrying 2.5 meters optical lens. Can it determine the color of your eyes?
asked Sep 19, 2014 in Physical Science by mony (120 points)

1 Answer

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To determine anything about eyes, it needs to be able to have a resolution at the scale of the size of eyes. The average distance between eyes is about 0.06 m. That gives an angular resolution of ||\theta=\frac {0.06}{250000}||.

The lens resolution is approximately ||\theta=1.22 \frac {\lambda}{D}||  

See http://en.wikipedia.org/wiki/Optical_resolution for explanations.

Putting all together, the spy satellite would be able to determine eyes for the light with wavelength 500 nm or shorter.
answered Sep 19, 2014 by PhysicsDude (21,750 points)
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