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NDA 1 2025 GAT, question 141

Topic: Physics

Q141

If the speed of light in carbon disulfide and vacuum is X and Y respectively, then

  1. (a) X<YX < YCorrect answer
  2. (b) X>YX > Y
  3. (c) X≥YX \geq Y
  4. (d) X=YX = Y

Solution.

Answer: (a) X<YX < Y

  1. For ordinary visible light, carbon disulfide has refractive index n>1n > 1.
  2. Since n=Y/Xn = Y/X, its light speed is X=Y/n<YX = Y/n < Y, the vacuum speed.