WAEC Physics 2025 Objective — Question 15
Question 15 of 51 from the West African Examinations Council (WAEC) Physics 2025 Objective paper, with the correct answer and a full explanation.
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The speed of light in medium A of refractive index 1.5 is 2.0×10⁸ ms⁻¹. Determine the speed of light in medium B of refractive index 1.2.
- A. 1.8×10⁸ ms⁻¹
- B. 2.5×10⁸ ms⁻¹Correct
- C. 2.7×10⁸ ms⁻¹
- D. 3.0×10⁸ ms⁻¹
Explanation
nₐvₐ = n_bv_b (since c = n×v is constant) → v_b = (nₐvₐ)/n_b = (1.5×2×10⁸)/1.2 = 2.5×10⁸ ms⁻¹.
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