Why does light bend when it enters glass?

Light bends when it enters glass because it changes speed, just like a car slows down when it goes from a highway to a street.

Imagine you're riding your bike on a smooth path, and suddenly the road gets bumpy. You slow down, right? That’s what happens to light: it moves faster in air than it does in glass. When it hits the glass, it slows down, and that makes it change direction, like a car turning a corner.

Think of light as a group of little runners moving across a field. If they all run straight on a flat path, they keep going straight. But if one side of the group hits a patch of wet grass (which makes them slow down), that part of the group lags behind, and the whole line bends toward the slower part.

That’s exactly what happens with light: the part of the wave that enters glass first slows down, pulling the rest of the wave along with it. That's why we see a bend, just like when you look at a straw in a glass of water and it looks bent!

So no magic, just speed changes and a little teamwork from light waves! Light bends when it enters glass because it changes speed, just like a car slows down when it goes from a highway to a street.

Imagine you're riding your bike on a smooth path, and suddenly the road gets bumpy. You slow down, right? That’s what happens to light: it moves faster in air than it does in glass. When it hits the glass, it slows down, and that makes it change direction, like a car turning a corner.