Define 1 dioptre of power of a lens.

Define I dioptre of power of a lens ?

Define the power of lens. What is the meaning of "the power of lens is 1 dioptre" if the power of a lens -2.0D, then what type of lens is that? when an object is kept at infinity from this type of lens, what is the size of the image formed.

Define 1 watt of power

Define power of a refracting surface. (Define the power of a lens).