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Two thin lenses of focal length 20 cm an...

Two thin lenses of focal length 20 cm and 25 cm are in contact. The effective power of the combination is :

A

4.5 D

B

18 D

C

45 D

D

9 D

Text Solution

Verified by Experts

The correct Answer is:
D
`P_1 = (100)/(20) = 5D, P_2 = (100)/(25) = 4D `
Effective power ` P = P_1+P_2`
` " " = 5+4 `
` " " 9D `
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