Lenses are usually made from glass or plastic ... It is refraction that makes some objects appear to bend when they are viewed through water, like the straw shown here. If the light hits the ...

These two defects are treated with spectacle lenses, which refract (bend) the light rays so that they do focus on the retina. Someone who is short-sighted can see near objects clearly, but cannot ...

This remarkable phenomenon was observed when a massive foreground galaxy cluster acted as a gravitational lens, bending and ...