twothin lenses of power +3.5D and -2.5D are placed in contact with each other. find the power and focal length of the lens combination

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Solution

let
P1 = +3.5 D
P2 = -2.5 D

the power of the lens combination would be
P = P1 + P2
so,
P = 3.5 - 2.5 = 1 D

the focal length, f = 1/P = 1 m = 100 cm

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twothin lenses of power +3.5D and -2.5D are placed in contact with each other. find the power and focal length of the lens combination

letP1 = +3.5 DP2 = -2.5 D the power of the lens combination would beP = P1 + P2so,P = 3.5 - 2.5 = 1 D the focal length, f = 1/P = 1 m = 100 cm

let
P1 = +3.5 D
P2 = -2.5 D

the power of the lens combination would be
P = P1 + P2
so,
P = 3.5 - 2.5 = 1 D

the focal length, f = 1/P = 1 m = 100 cm