Q51 / 270 · NDA 2025 (Phase 2) · General Ability
The focal length of a concave lens is 0·5 m. The power of the lens is
- A+0·5 D
- B−0·5 D
- C+2·0 D
- Correct answerD−2·0 D
Solution
The focal length of a concave lens is taken as negative.
$f = -0\cdot5$ m
The power of a lens is given by $P = \dfrac{1}{f}$
$P = \dfrac{1}{-0\cdot5} = -2\cdot0$ D
Answer: −2·0 D
$f = -0\cdot5$ m
The power of a lens is given by $P = \dfrac{1}{f}$
$P = \dfrac{1}{-0\cdot5} = -2\cdot0$ D
Answer: −2·0 D
Hence, the correct answer is option: 'D'.