Lesson: Chapter 5 — Optics

Seeing by light 3 of 3

Rays and beams

To show which way light travels, it is drawn as a straight line with an arrow on it: a ray.

The arrow is not optional

A line without an arrow does not say which way the light is going. On every ray you draw, the arrowhead must be there.

Beam

A group of rays is called a beam.

Parallel beam

The rays run side by side, never meeting.

Converging beam

The rays come together towards one point.

Diverging beam

The rays spread apart from one point.

A parallel beam meeting a concave mirror and converging to one point after reflection — both a parallel and a converging beam in one picture.

The beam arriving is parallel; the beam leaving the mirror is converging, and after the meeting point it becomes diverging.