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NDA 2 2025 GAT, question 53

Topic: Physics

Q53

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

  1. (a) 2×103 A.U.2\times 10^{3}\text{ A.U.}
  2. (b) 2×104 A.U.2\times 10^{4}\text{ A.U.}
  3. (c) 2×105 A.U.2\times 10^{5}\text{ A.U.}Correct answer
  4. (d) 2×106 A.U.2\times 10^{6}\text{ A.U.}

Solution.

Answer: (c) 2×105 A.U.2\times 10^{5}\text{ A.U.}

  1. A parsec is the distance at which 1 AU subtends one arcsecond.
  2. Since one radian is about 206265 arcseconds, 1 pc≈206265 AU≈2×10⁵ AU.
  3. This order-of-magnitude check selects (c).