system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If when light ray travels from one medium to other, it's speed decreases/increases, why does the direction of the light ray change?

The question should be self-explanatory, But if any explanation needed, I'll do the needful.
gpt
The easiest way to visualise it is to think about a remote control car driving from concrete on to sand at an angle. The wheels that hit the sand first would slow immediately, causing the car to turn. This is essentially the same way it works with light, as the wave enters at an angle, one "side" of the wave will hit the new material first and will slow down or speed up before the other side does.