How does light propagate?

Light moves through space like a line of kids passing a ball from one to another.

Imagine you're playing tag outside on a sunny day. The sun is like a friend who throws a ball (light) toward you. That ball travels all the way until it hits you, that's how light gets from the sun to your eyes, or from a lamp to a toy.

Light travels in straight lines, just like when you walk from one end of the playground to the other. If there’s nothing blocking its path, it keeps going until it hits something, like a wall, or your eye.

Sometimes, light bounces off things, like when a ball hits a wall and comes back toward you. That's how you can see your reflection in a mirror, the light from the room bounces off the mirror and into your eyes.

If light passes through something clear, like water or glass, it keeps going, but it might slow down, just like when you walk through deep snow and move slower than on the playground.