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

NDA 2025 · General Ability · General Science

One parsec in astronomical units (A.U.) is about

One parsec in astronomical units (A.U.) is about

Options

  1. A2×1032 \times 10^3 A.U.
  2. B2×1042 \times 10^4 A.U.
  3. C2×1052 \times 10^5 A.U.
  4. D2×1062 \times 10^6 A.U.

Correct answer

C. 2×1052 \times 10^5 A.U.

Step-by-step solution

One parsec is defined as the distance at which an arc of length one astronomical unit (A.U.) subtends an angle of one second of arc.

\theta = 1'' = \left(\dfrac{1}{3600}\right)^{}^{\circ} = \dfrac{\pi}{180 \times 3600} \text{ rad}

r=lθ=1 A.U.π180×3600r = \dfrac{l}{\theta} = \dfrac{1 \text{ A.U.}}{\dfrac{\pi}{180 \times 3600}}

r=180×3600π A.U.≈206265 A.U.r = \dfrac{180 \times 3600}{\pi} \text{ A.U.} \approx 206265 \text{ A.U.}

r≈2×105 A.U.r \approx 2 \times 10^5 \text{ A.U.}

Answer: 2×1052 \times 10^5 A.U.
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