Question

Determine power of a convex lens with f 25 and concave f=20

Answer 1

needs you to know that powers of lenses are additive.

So, we will first find powers of the two lenses, and then add them to get the final power.

F1= -25 cm = - 0.25 m

P1= 1/F1 = -4D

F2 = 20 cm = 0.2 m

P2 = 1/F2 = 5 D

So , total Power will be 1D.

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