Define the term refractive index of a medium in terms of velocity of light.

Explanation

**Step-by-Step Solution:**

1. **Understanding Refractive Index**: The refractive index is a measure of how much the speed of light is reduced in a medium compared to its speed in a vacuum.

2. **Definition**: The refractive index (denoted as \( n \)) of a medium can be defined mathematically as:
\[ n = \frac{c}{v} \]
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