An optician prescribes a lens of power =-0.5 dioptre. The
corresponding lens must be a

When an optician prescribes a - 5D lens, what does it mean?

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 ?

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 lens required for correcting (1) distant vision and (2) near vision ?

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 near vision?