A) \[+9\text{ }cm\]
B) \[-18\text{ }cm\]
C) \[-9cm\]
D) \[+18cm\]
Correct Answer: D
Solution :
Focal length of combination \[\frac{1}{F}=\frac{1}{{{F}_{1}}}+\frac{1}{{{F}_{2}}}\] \[=\frac{1}{9}-\frac{1}{18}\] \[=\frac{2-1}{18}=\frac{1}{18}\] \[F=+18\,cm\]You need to login to perform this action.
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