COMEDK · Physics · 25. Ray Optics
Two converging lenses of focal length \(20 \mathrm{~cm}\) and \(40 \mathrm{~cm}\) are placed in contact. The effective power of the combination is
- A \(5.25 \mathrm{D}\)
- B \(7.25 \mathrm{D}\)
- C \(2.75 \mathrm{D}\)
- D \(7.5 \mathrm{D}\)
Answer & Solution
Correct Answer
(D) \(7.5 \mathrm{D}\)
Step-by-step Solution
Detailed explanation
The power of a lens is given by \(P = \dfrac{1}{f}\), where \(f\) is the focal length in meters. For two thin lenses in contact, the effective power \(P\) is the sum of the individual powers \(P_1\) and \(P_2\). Given \(f_1 = 20 \text{ cm} = 0.2 \text{ m}\) and…
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