Question:
What is the S.I. unit of power of lens?
What is the S.I. unit of power of lens?
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Power of lens increases when focal length decreases.
Updated On: Oct 27, 2025
- cm\(^{-1}\)
- m
- cm
- Dioptre
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The Correct Option is D
Solution and Explanation
Step 1: Understanding power of a lens.
The power of a lens is defined as the reciprocal of its focal length (in meters).
\[ P = \frac{100}{f \, (\text{in cm})} = \frac{1}{f \, (\text{in m})} \] Step 2: Unit of power.
Since focal length is measured in meters, the unit of power is \( m^{-1} \). This unit is given a special name "Dioptre (D)".
Step 3: Conclusion.
Therefore, the SI unit of power of a lens is Dioptre.
The power of a lens is defined as the reciprocal of its focal length (in meters).
\[ P = \frac{100}{f \, (\text{in cm})} = \frac{1}{f \, (\text{in m})} \] Step 2: Unit of power.
Since focal length is measured in meters, the unit of power is \( m^{-1} \). This unit is given a special name "Dioptre (D)".
Step 3: Conclusion.
Therefore, the SI unit of power of a lens is Dioptre.
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