Concave Mirrors

You must have seen the curved part inside torch? What is the function of that silvered coating in it? Just try to see your face through the internal curved side of spoon. What did you observed there? We can change the size of image produced by mirror by selecting desired shape of mirror. Spherical mirrors which bulges (curved) internally such as its bulged surface becomes reflecting, called as concave mirror.

As shown in fig. the spherical mirror whose externally bulged surface is polished such that internally bulged surface become reflecting is known as concave mirror. They are cut from sphere of glass and polished with certain materials so that it acts as reflecting surface.

Concave mirrors can form image on the screen, such image is called as real image. These images appear inverted. i.e. when you hold candle in front of concave mirror as sufficiently longer distance, image of flame of candle obtained on screen will be smaller and inverted (exactly opposite to its actual position.) We may felt that the object is rotated by 1800. At some instances, concave mirror forms very big image and its position is also as same as the object i.e. not appear to be rotated. Such images are called virtual and erect image.

When parallel beam of light falls on concave mirror, after reflection all rays passes through the same point, this point is known as focus of mirror. Due to this ability concave mirrors are also called as converging mirror. See the diagram below.

Now let’s discuss some important conditions of image formation due to concave mirrors.

  • When object is placed near to concave mirror, it produces bigger size image of the object. Image is real and inverted.
  • When object is kept far away from mirror, it produces smaller size image of object.Image is real and inverted.
  • When object placed very close to mirror, it produces large size of image.

As this image can’t be produce on screen it is virtual and erect.

Listed below are some important applications of concave mirror.

 

  • Shaving and Makeup Mirrors: For shaving or makeup purpose, concave mirrors are held close to face so that highly magnified image of face can be obtained, which helps us to make clean shave or perfect makeup.
  • Dentist mirrors: If you have toothache, and you are really in trouble, you need to visit a Dentist. He can diagnose your problem by observing your mouth by holding a concave mirrors close to your mouth.
  • Headlights of vehicles or torch: For safe driving during night time we need sharp and focused beam of light, which can be obtained by fixing a bulb at centre of concave shaped silvered polished mirror.

Q. What do you mean by concave mirror?

Ans: Spherical mirrors which bulges (curved) internally such as its bulged surface becomes reflecting, called as concave mirror.

Q. What types of images can be produced by concave mirror?

Ans: Concave mirror can produce real image and virtual image of object by changing the distance between object and mirror.

Q. What do you mean by inverted image?

Ans: When image of object on screen is appear to be rotated by 1800, and then it is termed as inverted image.

Q. State some day to day life application of concave mirror.

Ans: Concave mirrors are used in shaving/makeup mirrors, dentist mirrors, headlights of vehicles and torches etc.

Q. Why concave mirror is also called as converging mirror?

Ans: When parallel beam of light falls on concave mirror, after reflection all rays passes through the same point, due to this property concave mirror is also known as converging mirror.


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