I've been doing some calculations on lenses, and i'm a little confused about some of the diagrams i've seen. Looking at a ray diagrams, I see the light passing through the lens, at one angle, and then converging on a focal point from there. Using snells law to calculate refraction through the materials, the concept of focal point is confusing me. If light enters one side of the lens, and refracts, wouldn't it refract in the opposite direction upon leaving the material(because it's not going from an area of lower wave velocity to higher)? Also, based on that, wouldn't there be some sort of lens configuration that allowed for a no focal point to exist, and light to continue at the same angle it entered, just more concentrated? My knowledge of optics is limited, so I apologize i'm asking an obvious question. I've searched for an answer all over the place and can't seem to find one. Thanks in advance.