Light is an energy type that allows us to perceive things. Light originates from a source and reflects from objects, which our eyes see, and our brain analyses this signal, allowing us to see.
Step 2: Fermat’s theorem
Fermat's law tells that, the light travels between two points in the path that can be completed in the shortest time period.
When light enters a new medium, it bends because it is still on the quickest path.