Index of refraction (n)

Definition

The index of refraction (n) is defined as the ratio of the speed of light in vacuum to its speed in another medium. It quantifies how much light slows down when passing through different materials.

Analogy

Imagine you are running on a track and suddenly enter a swimming pool. Your speed will decrease because water slows you down. Similarly, when light passes from air to a denser medium like water or glass, its speed decreases due to the higher index of refraction.

Related terms

Snell's Law: A formula that relates the angles of incidence and refraction for waves passing through different media.

Total internal reflection: The complete reflection of a wave back into its original medium when it encounters an interface at an angle greater than the critical angle.

Dispersion: The separation of white light into its component colors (wavelengths) as it passes through a prism or other transparent material.