I was reading a book of mine that states that if water had a negative index of refraction then we'd see fish suspended in air. Why? Should not we see still it in water but far away respect to its real position?
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1$\begingroup$ Can you reference the book? $\endgroup$– Guillermo Abad LopézCommented Jul 15, 2022 at 1:04
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$\begingroup$ Fill a bowl with water. Hold a pencil half in and half out of the water, making an angle of about 45 degrees with the surface. Look down the length of the pencil. When I try that experiment, the pencil seems to bend upward (i.e., the submerged end appears to be closer to the surface than it really is.) My expectation is that if the water in the bowl had a negative index of refraction, then the pencil would seem to bend the opposite way—the submerged end would appear to be deeper than it really was. But, I don't know for sure whether that's a sound argument. $\endgroup$– Solomon SlowCommented Jul 15, 2022 at 1:54
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$\begingroup$ @SolomonSlow I think that's for a positive index of refraction less than one. (You can do the experiment by going underwater in your favorite swimming pool and looking up through the surface.) $\endgroup$– rob ♦Commented Jul 16, 2022 at 10:11
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Your source is wrong. The fish will not appear to float but the apparent position will change:
The calculated ray-tracing image of a metal rod in an empty glass (left) is compared to a metal rod in a glass of water with index of refraction n = 1.2 (center), showing ordinary refraction effects. Replacing the water by a fictitious negative-refractive-index material (right) with n = -1.2 causes unusual refraction effects.
Source: LaserFocus World, April 30, 2006 https://www.laserfocusworld.com/optics/article/16546742/optics-negativeindex-materials-form-strange-images
answered Jul 16, 2022 at 2:00