A doctor has prescribed a corrective lens of power +1.5 D . Find the focal length of the lens . Is the prescribed lens diverging or converging?

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?

Is the focal length of a lens the same for lights of all colors ?

Find the focal length of a lens of power −2.0 D. What type of lens is this?

A man used a concave lens of focal length 20cm.Find the power of the lens.

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 distant vision?

a convex lens of power 3.5D is placed in contact with a concave lens of power -1.5D. Find the effective focal length of the combination.