A) + 9 cm
B) -18 cm
C) -9 cm
D) +18 cm
Correct Answer: D
Solution :
Focal length of combination \[\frac{1}{F}=\frac{1}{{{F}_{1}}}+\frac{1}{{{F}_{2}}}\] \[=\frac{1}{9}-\frac{1}{18}=\frac{2-1}{18}=\frac{1}{18}\] \[F=+10\,cm\]You need to login to perform this action.
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