CBSE · Class 10 · Science · Light – Reflection and RefractionThe power of a lens is -2.5 D. What is its focal length?
Step-by-Step Solution
Power of a lens (P) is given by P = 1 / f(in meters). Therefore, f = 1 / P = 1 / (-2.5) = -0.4 m, which is equal to -40 cm. Therefore, option A is correct.
Detailed Options Breakdown
Option : -40 cm (Correct Answer)
Correct choice. Refer to the step-by-step verified solution guidelines above for details.
Option 1: +40 cm
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Light – Reflection and Refraction.
Option 2: -25 cm
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Light – Reflection and Refraction.
Option 3: +25 cm
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Light – Reflection and Refraction.
💡 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.