A) - 1.5
B) - 6.5
C) + 6.5
D) + 6.67
Correct Answer: A
Solution :
\[\frac{1}{f}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}\] \[\frac{1}{f}=\frac{1}{40}+\frac{1}{-\,25}\] \[\Rightarrow \] \[f=\frac{-\,40\times 25}{40-25}\] \[\Rightarrow \] \[f=-\,66.67\,cm\] \[\therefore \] \[P=\frac{1}{f(in\,m)}=-\frac{100}{66.67}=-1.5\,D\]You need to login to perform this action.
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