The refractive index of water is 4/3. The speed of light in water is: MCQ with Answer and Explanation

The refractive index of water is 4/3. The speed of light in water is:
A. 4×10⁸ m/s
B. 1.5×10⁸ m/s
C. 3×10⁸ m/s
D. 2.25×10⁸ m/s
Answer: Option D
Solution (By JKExamLibrary)
Refractive index n = c/v, where c = 3×10⁸ m/s (speed in vacuum). Thus v = c/n = (3×10⁸)/(4/3) = 3×10⁸ × 3/4 = 9/4 × 10⁸ = 2.25×10⁸ m/s. This direct formula application is fundamental in optics. Memory aid: 'Higher n ⇒ slower light in medium'. Competitive exams frequently test this calculation with common refractive indices (water 4/3, glass ~1.5). Always use c = 3×10⁸ m/s unless specified otherwise, and ensure unit consistency (m/s here).

This question belongs to: Science Physics

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