CBSE · Class 10 · Science · Light – Reflection and RefractionDefine the power of a lens and state its SI unit.
Step-by-Step Solution
The power of a lens is quantitatively defined as the degree of convergence or divergence of light rays achieved by the lens. Mathematically, it is expressed as the reciprocal of its focal length measured in meters, given by the formula P equals 1 divided by f in meters. The standard SI unit of the power of a lens is the dioptre, represented by the capital letter D. One dioptre is defined as the power of a lens whose focal length is exactly one meter. A convex lens has positive power, while a concave lens has negative power.
💡 Study Guide: This question tests core syllabus concepts from Light – Reflection and Refraction. For formulas, key summaries, and mock exam reference guides, read the full Light – Reflection and Refraction Revision Notes.