# 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

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 $\theta=1.22 \frac {\lambda}{D}$