Question

Dioptre is the unit of

• A. Refractive index
• B. Focal length
• C. Radius of curvature
• D. power of the lens

Answer 1

The Correct Option is D

Correct answer: power of the lens 

Explanation:
The dioptre (D) is the SI unit of the power of a lens. It indicates the ability of a lens to converge or diverge light. 

Mathematically, power \( P \) is given by: \[ P = \frac{100}{f} \] where \( f \) is the focal length of the lens in centimeters. 

- If \( f \) is in meters, then: \[ P = \frac{1}{f} \quad (\text{in dioptres}) \] 
- A lens with focal length of 1 meter has power of 1 dioptre. 

Hence, the correct answer is: power of the lens.