Question

two lenses of power-2.0 D and + 1.5 D are combined together What is the focal length of the combination​

Answer 1

Answer:

-0.5D

focal length -200cms

it's simple additional expression

just do it and u will get -0.5D

then we know

power = 1/focal length in metres

so

-0.5= 1/f

or f = -1000/5 (1m = 100cm)

or f = -200 CMS