Question 159 of 295
An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is . Focal length of each of the convex lens is :
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Answer: (A)
We know that
given all lenses are identical
$\begin{aligned}
& \therefore 5 P=25 D \\
& \therefore P=5 D \\
& \therefore \frac{1}{f}=5 \Rightarrow f=\frac{1}{5} \mathrm{~m}=20 \mathrm{~cm}
\end{aligned}$
Hence option (1)
given all lenses are identical
$\begin{aligned}
& \therefore 5 P=25 D \\
& \therefore P=5 D \\
& \therefore \frac{1}{f}=5 \Rightarrow f=\frac{1}{5} \mathrm{~m}=20 \mathrm{~cm}
\end{aligned}$
Hence option (1)
