A) \[F=-20cm,\,P=-5\,D\]
B) \[F=-40cm,\,P=-5\,D\]
C) \[F=-40cm,\,P=-2.5\,D\]
D) \[F=-20\,cm,\,P=-2.5\,D\]
Correct Answer: C
Solution :
\[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\] \[\frac{1}{f}=\frac{1}{-20}-\left( -\frac{1}{40} \right)=\frac{-2+1}{40}=-\frac{1}{40}\] \[f=-40\,cm\] \[P=-\frac{200}{0.40}=-2.5\,D\]You need to login to perform this action.
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