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The speed of light in vacuum is approximately:
A3 × 10⁸ m/s — the maximum speed attainable in nature
B3 × 10⁶ m/s
C1.5 × 10⁸ m/s
D2.5 × 10¹⁰ m/s
Answer & Solution
Correct answer: A. 3 × 10⁸ m/s — the maximum speed attainable in nature
**c = 2.99792458 × 10⁸ m/s** (exact, by SI definition since 1983) ≈ **3 × 10⁸ m/s**. The **upper speed limit in nature** (special relativity). Light slows in matter: v = c/n.
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