One dioptre is……………of focal length……… .

The power of a lens is 2 dioptre its focal length will be…. .

If the power of a lens is 4 dioptres , find its focal length.

If the power of a lens is 4 dioptres , find its focal length.

The power of a convex lens is 2.5 dioptres. Find the focal length.

A person needs a lens of power -5.5 dioptres for correcting his distant vision, for correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision and (ii) near vision ?