Can the absolute value of refractive index of a medium be less than unity ?

Explanation

To determine whether the absolute value of the refractive index of a medium can be less than unity, we can follow these steps:

### Step 1: Understand the Definition of Refractive Index
The refractive index (n) of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in that medium (v). Mathematically, this is expressed as:
\[ n = \frac{c}{v} \]

### Step 2: Analyze the Speeds of Light
In vacuum (or air, which is very close to vacuum), the speed of light is at its maximum value, approximately \( c = 3 \times 10^8 \) meters per second. When light travels through any medium (like water, glass, etc.), its speed decreases, meaning \( v < c \).
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