# Why light takes the quickest path?

Light is a form of energy that enables us to see things. Light starts from a source and bounces off objects which are perceived by our eyes and our brain processes this signal, which eventually enables us to see.

The shortest path need not be the quickest path. Since light is always in a hurry, it bends when it enters a different medium as it is still following the quickest path. This phenomenon of light bending in a different medium is called refraction.

## Fermat’s theorem

The Fermat’s principle of least time is used to understand how light rays travel. According to this principle, the path taken by a ray of light between two points is the path that can be taken in the shortest time period, but not the shortest path.

• The principle of least time: Light always takes the quickest path between any two points which may not be the shortest path.
• Rectilinear propagation of light and the law of reflection [∠i=∠r] can be validated by Fermat’s principle of least time.