Question

two thin lenses of power + 3.5 and -2.5 D are placed in contact. find the power of the focal length of the lens combination

Answer 1

Dear student
P₁ = 3.5D, P₂= -2.5 D

when two thin lenses place in contact then power of combination is sum of the poers of two thin lenses

Hence power of combination is P=3.5-2.5 = 1 D

and focal lenth F= 1/P = 1 m = 100 cm

regards