Question

Two thin lenses of focal lengths +20cm and -30cm are placed in contact.The effective power of combination is

Answer 1

Answer:

+1.66D

Explanation:

Answer 2

Answer:

Explanation:

effective power =  Peff  = P1 +P2+P3 +................

so from above case

P eff =  1/f1+ 1/ f2

          =  1/20 - 1/ 30

           = 1/60 D or .0166D

Hope it helps ...............