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KCET · Physics · Ray Optics

Two thin lenses have a combined power of +9D. When they are separated by a distance of \(20 \mathrm{~cm}\), their equivalent power becomes \(+\frac{27}{5}\) D. Their individual powers (in dioptre) are

  1. A 1,8
  2. B 2,7
  3. C 3,6
  4. D 4,5
Verified Solution

Answer & Solution

Correct Answer

(C) 3,6

Step-by-step Solution

Detailed explanation

Given,
\[
\begin{gathered}
P_{1}+P_{2}=9 \\
P=P_{1}+P_{2}-d P_{1} P_{2} \\
\frac{27}{5}=9-\frac{20}{100} \times P_{1} P_{2}
\end{gathered}
\]
Hence, the above equation is correct for
\[
P_{1}=3 \text { and } P_{2}=6 \text {. }
\]