When swimming underwater, why is vision blurred when you open your eyes, but clear when wearing swimming goggles? Eyesight Read more from Chapter Light

Some people are unable to see some colors due to an inherited condition known as color blindness. John Dalton (1766-1844), a British chemist and physicist, described color blindness in 1794. He was color blind himself, and could not distinguish red from green. Many color-blind people do not realize that they cannot distinguish colors. This is potentially dangerous, particularly if they cannot distinguish between the colors of traffic lights or other safety signals. Those people who perceive red as green and green as red are known, appropriately, as “red-green color blind.” Other color-blind people are only able to see black, gray, and white. It is estimated that 7% of men and 1% of women are born color blind.

Although the eye’s lens changes shape to focus images on the retina, most of the refraction of light takes place during light’s transition from air to the cornea. When water is substituted for air, the angles through which light is refracted is reduced, producing a blurred image on the retina.