Ch 10 - Light: Mirrors and Lenses8th Science

Incident Ray: The incoming ray of light that strikes the reflecting surface.
Reflected Ray: The ray of light that bounces back from the reflecting surface.
Normal: An imaginary reference line drawn exactly at a $90^\circ$ angle (perpendicular) to the reflecting surface at the exact point of incidence.

The Law: The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same geometric plane.

The Proof: Shine a light on a piece of paper lying flat on a table. If you bend the paper downward over the table's edge, the reflected ray disappears on the bent portion because it moves out of the original plane. It only reappears when the paper is flattened back into a single 2D plane.

Regular Reflection: Occurs on smooth, polished surfaces (like mirrors). Parallel incident rays reflect as strictly parallel rays, forming clear and sharp virtual images.

Diffused (Irregular) Reflection: Occurs on rough, uneven surfaces (like paper, wood, or cloth). Parallel incident rays hit microscopic bumps and scatter in different directions, meaning no clear image is formed.

Note: Diffused reflection still perfectly obeys the laws of reflection at each individual microscopic point of incidence.