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Engineering Exams RRB-JE JE (Junior Engineer) CMA (Chemical and Metallurgical Assistant) DMS (Depot Material Superintendent) CS (Chemical Supervisor - Research) MS (Metallurgical Supervisor - Research) 2019 24.05.2019 Paper-1 Shift-1 Easy +1 -0.33 General Science
What is the speed of light in air?
Correct Answer: B. 3 x 10^8 m/s
Explanation: The speed of light in a vacuum is a fundamental physical constant approximately equal to 3 x 10^8 m/s (exactly 299,792,458 m/s). While light slows down slightly when passing through transparent media like air due to the refractive index, this change is minimal—roughly 0.03% slower than in a vacuum. Therefore, for most scientific calculations and general contexts, the speed of light in air is approximated as 3 x 10^8 m/s. Based on the provided options, 3 x 10^8 m/s (Option B) is the correct standard approximation.
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