Today we can see things clearly even after having defects in our eyes and that is possible because of the lenses. There are different types of lenses, but ever wondered what is the story behind these pieces of glasses?

Definition of Lens

In Physics, the lens is defined as the transparent piece of glass which is used for the formation of an image of an object by focusing the rays of light that are reflected from the object. The lens is usually circular in shape and has two polished surfaces with either of them curved. The curved surface can be concave or convex. These are known as a concave lens and a convex lens.

Production of Optical Lenses

For the manufacture of lenses, glass slabs are used. These slabs are cut into desired shapes with the help of either slitting disk or with glass saw. The other way of manufacturing lenses is by using heat treatment. The glass slab is exposed to heat which is then rolled into a round shape and is pressed in a mould of desired shape and size.

Principles of Lens

The main purpose of the lens is to increase the focus as the light travels slower in the lens which reduces the refraction of light while entering as well as while leaving the lens. The classification of the lens is based on their surfaces:

  • Biconvex
  • Biconcave
  • Plano-convex
  • Plano-concave
  • Concavo-convex
  • Convexo-concave

Uses of Lens

Contact lenses, eyeglasses are single lenses that are used for obtaining the image. Compound lenses find applications in microscopes, telescopes, and in cameras.

Fun Experiment

This section involves a fun experiment that can be tired at home. The experiment is of making a lens with the help of water. Following are the steps that need to be followed:

  • Take an old newspaper, clear plastic and an eye-dropper.
  • Now place the newspaper on the tabletop.
  • On this place the clear plastic.
  • To place a small drop of water on this setup, take an eye-dropper and slowly place a small amount of water on the plastic.
  • Now you see that the letters in the newspaper appear bigger than their usual size.
  • This is how a water lens is made.

Interesting Fact

Another interesting fact about the lens is that there was a first camera manufactured without the use of the lens and that camera is known as a pinhole camera. Pinhole cameras are used to witness the solar eclipse. Besides, it is easy to make a pinhole camera. So, how to make a pinhole camera?


Materials required for the making of a pinhole camera are:

  • Pencil
  • Empty box with a lid
  • Knife
  • Scissors
  • Ruler
  • Wax paper
  • Tape
  • Blanket


Following are the steps that need to be followed:

  • Use the pencil to mark a point on the empty box and make a small hole on the mark.
  • Now cut out a small square from the box on the other side with the help of a knife. The size of the square should be 2 inches.
  • Take the wax paper and cut a square of the size 3 inches on each side with the help of scissors.
  • Place the wax paper on the hole that is made on the box and seal it with the help of a tape.
  • Now take the box to a room which is lit dim and turn on the lamp which is placed at 5 feet away from the box.
  • Hold the box such that it is at arm’s length from your arms and don’t forget to cover yourself with the blanket.
  • You will see an upside-down image of the lamp.


Interested to learn more about histories of other equipment that are used in Physics, stay tuned with BYJU’S.


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