What are the different types of mirrors?

Mirrors have been in use ever since ancient times. Can you imagine a day in your life without a mirror? Archaeological evidences have established that mirrors made of polished metal were in use as long back as the Iron Age. The Egyptians began using silver and bronze mirrors by 2500 B.C. A mirror is made from a sheet of glass whose back is coated with a thin layer of silver or aluminium. It produces images by reflection. These mirrors obey the laws of reflection. A ray of light striking the mirror and is reflected into our eyes. The kind and size of the images depend on the shape and structure of the mirror. Do you know how many types of mirrors are there? Mirrors may have a flat or a curved surface. A flat mirror is called a plane mirror, and the image seen in a plane mirror is called a virtual image. Although we can see it, it cannot be projected onto a screen and the image appears to be formed behind the mirror. The image in a plane mirror is erect but laterally inverted, i.e. the righthand side of an object becomes the left-hand side in the image and vice versa. The image is always of the same size as the object. The plane mirrors are used in homes for seeing oneself, decorative purposes and in many optical instruments. There are two different types of curved mirrors — convex and concave. The convex mirrors curve outwards and concave mirrors inwards. The image in a convex mirror is always smaller than the object. The image is erect and virtual. Convex mirrors are used as view mirrors in automobiles. They allow the driver to see a larger area of the road behind him. The image in a concave mirror depends on how far the object is from the mirror and the focal length of the mirror. If the object is placed close to the mirror, the image is virtual, erect and magnified. A magnified image is larger than the object. Since they have magnifying properties, the concave mirrors are used as shaving mirrors. If the object is beyond a certain distance from the mirror, the nature of image changes. It becomes smaller than the object and turned upside down. The image is formed in front of the mirror and is said to be real. A real image can be projected on to a screen.

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