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AP EAMCET · PHYSICS · Ray Optics

Two lenses of powers \(-1.75 \mathrm{D}\) and \(+2.25 \mathrm{D}\) are placed in contact. The focal length of the combination is

  1. A \(100 \mathrm{~cm}\)
  2. B \(50 \mathrm{~cm}\)
  3. C \(200 \mathrm{~cm}\)
  4. D \(150 \mathrm{~cm}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(200 \mathrm{~cm}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{P}=\mathrm{P}_1+\mathrm{P}_2=-1.75+2.25=0.5 \mathrm{D}\) \(\begin{aligned} & \Rightarrow \frac{1}{\mathrm{f}_{\text {net }}}=0.5 \\ & \Rightarrow \mathrm{f}_{\text {net }}=2 \mathrm{~m}=200 \mathrm{~cm}\end{aligned}\)