https://modarchive.org/index.php?request=view_by_moduleid&query=185492

https://modarchive.org/index.php?request=view_by_moduleid&query=185492

https://modarchive.org/index.php?request=view_by_moduleid&query=185492

https://modarchive.org/index.php?request=view_by_moduleid&query=185492

https://modarchive.org/index.php?request=view_by_moduleid&query=185492

Light rays bend when they travel from one medium to another; the amount of bending is determined by the refractive indices of the two media. If one medium has a particular curved shape, it functions as a lens. The cornea, humours, and crystalline lens of the eye together form a lens that focuses images on the retina. The human eye is adapted for viewing in air. Water, however, has approximately the same refractive index as the cornea (both about 1.33), effectively eliminating the cornea's focusing properties. When immersed in water, instead of focusing images on the retina, they are focused behind the retina, resulting in an extremely blurred image from hypermetropia.[2] This is largely avoided by having an air space between the water and the cornea, trapped inside the mask or helmet.