Why can’t most people see clearly underwater?


Solution. Posted on Tuesday, November 11, 2014.

An eye refracts incoming light onto the retina. The cornea and aqueous bend light that enters the eye, pre-focusing an image before it reaches the eye’s lens, because of their refractive index differs from that of air. So, the light can be bent first at the surface of the eye, and again at the eye’s lens. The refractive indexes of water and the cornea are similar and light doesn’t bend at all when it enters the eye, if it comes from the water. The light is bent only by the eye’s lens, so that the image is not focused on the retina, but somewhere behind the retina.

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