Explanation:
Speed of light ≈ 3×10⁸ m/s, sound ≈ 340 m/s. Light reaches almost instantly, sound takes time. So thunder heard after lightning. Time delay gives distance: d = v_sound × t.
Explanation:
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).
Explanation:
Ship is made of steel (density > water) but hollow shape makes average density (including air) less than water. Displaced water weight equals ship's weight, buoyancy holds it up.
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