Tag Archives: refractive index

Why can’t we see under water? And how come penguins can?

One of my most indelible early memories is of participating in a near-drowning incident when I was 8 years old. This was in a lake, near the shore, in water less than three feet deep. A life jacket somehow ensnared my legs, suspending them near the surface and trapping my head under water. Before losing consciousness I saw spidery patterns of light rippling over the sand a few inches from my face, an image that lodged itself with vivid permanence in the inner recesses of my brain.

Or so I have always thought. Last night at a family dinner my dad disputed the accuracy of this visual memory. The human eye is incapable of focusing properly under water, he said, because the refractive index of water is so different from that of air. This led to a prolonged argument, my position fueled by better wine than science: eyes must be able to see under water because a) I remember doing so, and b) what about pearl divers?, and c) what about amphibious creatures like seals and otters? Continue reading

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