A) - 1.5 D
B) - 6.5 D
C) + 6.5 D
D) + 6.67 D
Correct Answer: A
Solution :
Focal length of the combination can be calculated as \[\frac{1}{F}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}\]\[\Rightarrow \frac{1}{F}=\frac{1}{(+40)}+\frac{1}{(-25)}\] \[\Rightarrow F=-\frac{200}{3}cm\] \[\therefore P=\frac{100}{F}=\frac{100}{-200/3}=-1.5\ D\]
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