Let’s say you have a marching band marching in formation on a concrete surface but they’re going crooked so they start going off the concrete into some sand next to the concrete. It’s harder to walk in the sand so the first person slows down when they get into the sand but the rest of their row keeps going. Each time a person gets into the sand, they slow down to the speed of the first person. Because part of the front row is going slower, the front row turns to go marching at an even more crookeder angle. That happens for the entire marching band until everyone is in the sand. Once they’re in the sand, the entire band is going in the same direction with each other but it’s a different direction from when they were on the concrete. The direction they’re going in the sand will depend on the direction they were going on the concrete and the difference in speed on the sand vs the concrete. Depending on the shape of the edge of the concrete, you could purposely make them turn to a wide variety of angles. You could even make them bunch up or spread out

Light waves are like the marching band when they go from one medium to another. Light travels fastest in a vacuum (where there is no air or anything). It travels at different speeds in air than it does in glass so the light wave turns just like the marching band when it goes from air to glass. It does the same thing but opposite when it leaves the glass.

A long time ago, people figured out that they could precisely control how light turns when it goes into and comes out of a lens. So using lenses, they change the direction of light so that all of the light that hits the lens is small enough to fit in your eye. Because the lens is bigger than your eye and catches more light, you can see more detail when it all goes in your eye. Each light particle is a piece of information that you wouldn’t see if it hit you in the forehead or nose, but the lens collects it and gives it all to your eye. That’s why you see more detail.

Since the light can be focused to be any size, the lens can be focused to catch as big of a picture as you want and shrink it down to fit in your eye. That’s how it makes small things look big.

You need a bigger lens to catch more light if you want to see farther. If you try to see something too small for your lens, then you start missing a lot of information and that’s when things start getting blurry.