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MHT CET · Physics · Ray Optics

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm . The power of combination is

  1. A \(-1.5 \mathrm{D}\)
  2. B -6.5 D
  3. C \(+6.5 \mathrm{D}\)
  4. D +1.5 D
Verified Solution

Answer & Solution

Correct Answer

(A) \(-1.5 \mathrm{D}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{P}=\frac{\mathrm{I}}{\mathrm{f}}=\frac{1}{\mathrm{f}_1}+\frac{1}{\mathrm{f}_2}\)
\(\mathrm{P}=\frac{1}{0.4}+\frac{1}{-0.25}=\frac{10}{4}-\frac{100}{25}=2.5-4\) \(=-1.5 \mathrm{D}\)