A person uses a lens of power `+3D` to normalise vision. Near point of hypermetropic eye is

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.

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 lens required for correcting(i) distant 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 ?