Without optical lenses, the world would be different. Maybe it wouldn't exist for us at all, because the eye also has a lens and vision is our main source of information. But lenses are also important in all kinds of cameras, many telescopes ...
We now know about the refraction of light when it moves from an optically rarer medium to an optically denser medium and back. Let's add spherical glass surfaces, i.e. lenses, to this image.