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NDA 2025
Exam
NDA
Year
2025
Subject
General Ability
Chapter
General Science

NDA 2025 · General Ability · General Science

The focal length of a concave lens is 0·5 m. The power of the lens...

The focal length of a concave lens is 0·5 m. The power of the lens is

Options

  1. A+0·5 D
  2. B−0·5 D
  3. C+2·0 D
  4. D−2·0 D

Correct answer

D. −2·0 D

Step-by-step solution

The focal length of a concave lens is taken as negative.

f=−0⋅5f = -0\cdot5 m

The power of a lens is given by P=1fP = \dfrac{1}{f}

P=1−0⋅5=−2⋅0P = \dfrac{1}{-0\cdot5} = -2\cdot0 D

Answer: −2·0 D
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