Many Faces of Light: As Newton Saw it, with Some Magic Tricks

Light rays chart out a straight path. Unless the rays bump into something, they are always straight lines.

There are two types of reflection. Specular reflection reflects all parallel rays at the same angle, like a mirror. Diffuse reflection reflects parallel rays at all different angles so that no image is transmitted, like a piece of paper.

When viewing an object reflected by a mirror, the rays appear to originate from behind the mirror.

Refraction occurs when light passes into a new material and starts to move at a different speed. If the ray hits the surface of the material at an angle, the ray will be bent.

Refraction can be understood through this analogy. Imagine that the fronts are rows of soldiers and the rays are lines of soldiers. The soldiers move more slowly through mud. If they approach it at an angle, then the soldiers on the left will reach the mud first, and slow down first. This will cause the lines of soldiers (the rays) to bend.

There are two basic types of lenses: the convex lens (or converging lens) and the concave lens (or diverging lens). Due to refraction, light rays bend as they pass into and out of the lens Convex lenses are shaped so that the rays converge together; concave lenses are shaped to spread rays apart.