Refraction and Dispersion

This section explores how light behaves when passing through different mediums and the phenomenon of dispersion.

Refraction is the bending of light that occurs when it passes between mediums of different densities. Key points about refraction include:

1. Light changes speed when moving between mediums of different densities.
2. When light enters a denser medium, it slows down and bends towards the normal.
3. When light enters a less dense medium, it speeds up and bends away from the normal.

Definition: The angle of refraction is the angle between the refracted ray and the normal in the second medium.

Ray diagrams for refraction show:

• Incident ray in the first medium $e.g., air$
• Normal at the boundary between mediums
• Refracted ray in the second medium $e.g., glass or water$
• Emergent ray when light exits the second medium

Highlight: Sometimes, light rays never leave the denser substance and are reflected internally. This phenomenon is called total internal reflection.

Dispersion occurs when white light passes through a prism:

1. White light separates into its component colors $the spectrum$.
2. Each color has a different wavelength and is refracted by a different amount.
3. Red light has the longest wavelength and is refracted the least, while violet has the shortest wavelength and is refracted the most.

Example: The colors of the spectrum can be remembered using the mnemonic "ROY G. BIV" $Red, Orange, Yellow, Green, Blue, Indigo, Violet$.

Vocabulary: The critical angle is the angle of incidence at which light is refracted along the surface between two mediums, beyond which total internal reflection occurs.

Understanding these principles of light, reflection, and refraction is crucial for various applications in optics, photography, and everyday life.