Question:
The power of a lens is 2:5 D. Its focal length is
The power of a lens is 2:5 D. Its focal length is
Updated On: Apr 5, 2025
- 10 cm
- 25 cm
- 30 cm
- 40 cm
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The Correct Option is D
Solution and Explanation
The power of a lens is related to its focal length \( f \) by the formula: \[ P = \frac{1}{f} \quad \text{where} \quad P \text{ is the power in diopters (D) and } f \text{ is the focal length in meters}. \] We are given that the power of the lens \( P = 2.5 \, D \). Using the formula, we can calculate the focal length \( f \) in meters: \[ 2.5 = \frac{1}{f}. \] Solving for \( f \): \[ f = \frac{1}{2.5} = 0.4 \, \text{m} = 40 \, \text{cm}. \]
The correct option is (D): 40 cm
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