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Science (086) — AI-generated practice question

AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.

Q1. [1] straightforward exam-ready
The power of a lens is –4.0 D. The focal length and type of lens are: (A) +25 cm, convex (B) –25 cm, concave (C) +40 cm, convex (D) –40 cm, concave
  1. A +25 cm, convex
  2. B –25 cm, concave
  3. C +40 cm, convex
  4. D –40 cm, concave
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer

(D) –25 cm, concave

$f = \frac{1}{P} = \frac{1}{-4.0} = -0.25\ \text{m} = -25\ \text{cm}$. Negative focal length indicates a concave (diverging) lens.

Explanation

Use $f = \frac{1}{P}$, always convert to cm. A negative power → negative focal length → concave lens. Examiners expect the formula, substitution, and correct identification of lens type.

Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.