If a glass medium has refractive index n = 1.5, what is the speed of light in this glass (speed of light in vacuum c = 3 x 10^8 m/s)?
Answer and explanation
Correct answer: D. 2.0 x 10^8 m/s
- Step 1: By definition, refractive index is n = c / v. Step 2. v = c / n = (3.0 x 10^8) / 1.5 = 2.0 x 10^8 m/s. Answer: 2.0 x 10^8 m/s. Why not the others: 1.5 x 10^8 m/s divides by 2; 4.5 x 10^8 m/s multiplies by 1.5 (exceeding c); 3.0 x 10^8 m/s is speed in vacuum.
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