For example, rear-view mirrors on a car allow you to see what's behind you before you back up. In addition to helping you make sure your hair looks nice before you head out to school or off to work, mirrors serve many important functions. They are flat and reflect the objects in front of them accurately, maintaining the same relative size and position of the objects reflected. The mirrors in most bathrooms are these types of mirrors, known as plane mirrors. Today, mirrors are usually made of clear glass that has been coated on one side with a thin film of metal, such as silver or aluminum. European glass makers began developing a process of coating clear glass with a thin layer of reflective metal in the 15 th and 16 th centuries. The modern mirrors you're familiar with are much more recent. Large pieces of polished metal, such as brass, were also used as mirrors, although these were very expensive. The first mirrors were likely polished stones, such as obsidian (a type of volcanic glass). If a smooth surface absorbs the photons, they can't bounce back and there will be no reflection.Īlthough calm, dark water has been used as a mirror since the beginning of time, people started making mirrors thousands of years ago. Of course, not all smooth surfaces act as mirrors. The words on the shirt appear backwards in the mirror. The mirror image is reversed, which you can easily see if you stand in front of a mirror with a shirt with words on it. Your eyes see these reflected photons as a mirror image. When photons - rays of light - coming from an object (your smiling face, for example) strike the smooth surface of a mirror, they bounce back at the same angle. The key factor is a smooth surface, because rough surfaces scatter light instead of reflecting it. Would you believe that mirrors have been around since the beginning of time? It's true! The first human beings ever to look into a calm, dark pool of water saw their reflections.ĭon't you wonder what their reactions were? Who are those people? And what are they doing in the water?!īasically, anything with a smooth surface that reflects almost all of the light that hits it - with only very little light absorbed or scattered - can be a mirror.
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