We can burn a piece of paper by focusing the sun rays by using a particular type of lens.
Name the type of lens used for the above purpose.

Name the type of lens used to correct eye defect.

The power of a lens is -5 D. Name the type of lens.

A virtual, diminished image is formed when an object is placed between the optical centre and the principal focus of a lens. Name the type of lens which forms the above image.

Name the type of waves which are used for sound ranging.

What type of lens is used to correct long sightedness ?

Name two types of devices used for removing particulate air pollutants.

The power of a lens is -5D. (i) Find its focal length. (ii) Name the type of lens.

Study the diagram given below and answer the questions which follow. The diagram is depicting a defect of the human eye. Name the type of lens used to correct short sightedness.

Which type of water can be used for human consumption?

Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens, a certain defect of vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens.