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 dioptres. What is the focal length of the required for correcting (i) distant vision, and (ii) near vision ?

A person needs a lens of power, -5.5 D for correcting his distant vision. For correcting his near vision, he needs a lens of power, + 1.5 D. What is the focal length of the lens required for correcting : (a) distant vision ? (b) near vision ? What type of lens is being used for correcting (i) distant vision, and (ii) near vision ?

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 + 3D for correcting his near vision and -3D for correcting his distant vision. Calculate the focal lengths of the lenses required to correct these defects.

Noopur needs a lens of power-4.5 D for correction of her vision. What are the causes of this defect?