Whether you are trying out a new dress or wondering if you are really going bald, the first thing you turn to look at is a mirror. From your car to your powder room, from telescopes to televisions, mirrors serve many important functions. This article highlights the types of mirrors, their uses and their structure.
Identification
A mirror is made by applying a reflective coating to a suitable base surface. Glass is considered the best substrate because of its rigidity, ease of fabrication and smooth finish. The reflective coating, usually aluminum, silver or gold, is applied to the back of the glass surface. The metal chosen for the coating determines the reflectivity of the mirror. Aluminum is the most inexpensive and the most commonly used coating. Silver and gold are more expensive and offer better reflectivity for visible and infrared wavelengths.
Function
Mirrors are extremely versatile in their function. They're used for cosmetic purposes in dressing rooms and bath rooms. They also provide rear view in automobiles. Mirrors are used for signaling in the military and during rescue operations. Microscopic mirrors are used in HD TVs. Telescopes and other optical instruments too use mirrors. Mirrors play an important role in interior decor. They are used to gather and reflect solar energy in systems that are powered by the sun. Different kinds of "fun mirrors" are used to amuse and entertain people.
Types
The most common type of mirror reflects most of the light that falls on it. Two-way mirrors or one-way glass let part of the light pass through and reflect part of the light. These are what one sees in stores where one reflective side is dark and the other reflective side is bright. Based on the shape, mirrors are classified as concave (like the inside of a bowl), convex (like a bowl turned upside down) and plane, or flat.
History
Polished stone mirrors were used as early as 6000 B.C.E. in Turkey. Polished copper and bronze were also used as mirrors in countries like Mesopotamia and China. The origin of metal coated glass mirrors dates back to first century C.E., invented in modern-day Lebanon. During the Renaissance period, European mirror makers began coating glass with a tin-mercury amalgam. In the 16th century, Venice became well-known for this type of mirror manufacturing. A German chemist, Justus von Liebig, invented the silver-glass mirror technology in 1835. Today, vacuum deposition is used to coat glass substrates with aluminum or silver.
Misconceptions
Superstitions abound across cultures when it comes to mirrors. In America, some believe that a dead person's soul gets trapped in a mirror, so, the custom of covering all mirrors during a wake is observed. People in parts of India believe that a broken mirror is a bad omen, so they discard a broken mirror immediately and brace themselves for a calamity. Legend has it that creatures that are not fully dead do not possess a soul and so have no reflection. This is the classic vampire test. Some cultures believe it is bad luck for two mirrors to face each other.
Scientifically speaking, a mirror is a piece of glass coated with a metal. How magical properties got associated with it is not known. It is more likely that because they were highly expensive and to ensure that they were handled with care, warnings about broken mirrors and bad luck started circulating. Or, perhaps, the reflective property of mirrors was fascinating to someone with a lively imagination who then originated tales about souls being trapped. It is also possible that because mirror pieces lying shattered on the floor are dangerous to people walking by, especially children, importance was placed on not breaking them and discarding broken pieces immediately. Whatever the reasons may be, the beliefs may seem ridiculous to some today, but they served a purpose during some period in history.
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