A plane mirror, while not a common term, is a common device that we use in several ways around the home, in our offices and in our vehicles. The plane mirror has a long history in civilized culture and has a hand in keeping drivers safe on our congested streets. This article will briefly cover the definition, history, properties, and uses of the plane mirror.
Plane mirrors are the common, everyday, flat mirrors that we see everywhere in our society. A plane mirror consists of a flat, two-dimensional surface that reflects the light coming from or reflecting off another object. When light rays strike this particular mirror, the angle of reflection (the light ray’s incoming angle) is equal to the angle of incidence (the light ray’s outgoing angle). The object reflected will appear to be behind the mirror’s surface at the identical distance away.
The ancient Egyptians and Greeks constructed plane mirrors out of polished metals like copper, bronze and brass. The Romans learned the art of glass making and coated the backs of these glass sheets with metal. During the Middle Ages, artisans used mercury mixed with tin to coat sheets of glass. The process evolved four hundred years later; during the 1800s, artisans perfected a process that coats the back of glass with metallic silver. The modern process involves layering molten aluminum or silver onto the back of a sheet of glass inside a vacuum.
Nowadays, one can find examples of plane mirrors everywhere. They are usually housed in a plain or fancy wooden or metal frame that's hung on a wall, and increasingly they are used as decorative accessories in homes. They can measure from less than an inch to several feet wide. People use them in the bathroom to comb their hair, brush their teeth, and shave their face. The family car has a plane mirror to see objects directly behind and to the left and right of the vehicle. Women around the world touch up their makeup with tiny hand held mirrors that they carry with them.
When a light ray strikes a plane mirror, it reflects at the same angle in which it struck the mirror, but the light ray will travel in the opposite direction from which it arrived. If the light ray hits the mirror at a 30-degree angle from the sky, it will reflect 30 degrees toward the ground. Imagine a pool table filled with colored balls, some solid, some striped. Each ball is a ray of light. Let us also say that the cue ball strikes the solid yellow ball and the ball rushes toward the far end of the table at a two-degree angle. When that ball hits the wall, it will bounce back (reflect) toward the shooter at a two-degree angle. Light works the same way.
Plane mirrors are widely used around the world. They began as polished sheets of metal and worked their way into our vehicles, homes, offices and places of entertainment around the world. Their reflective properties have not only been used to help us make sure we're clean and looking our best, but plane mirrors give drivers an extra layer of security by reflecting what is behind and around them.
