Question

What is called absolute refractive index ?

Hint:

Remember that the term "absolute" signifies that the reference medium is a vacuum. If the reference is any other medium, it's called the "relative refractive index". The formula \( n = c/v \) and the fact that \( n \geq 1 \) are crucial points to recall.

Answer 1

The absolute refractive index of a medium is a measure of how much the speed of light is reduced inside that medium compared to its speed in a vacuum. 
\[\begin{array}{rl} \bullet & \text{Definition: It is defined as the ratio of the speed of light in a vacuum (\(c\)) to the speed of light in the given medium (\(v\)). } \\ \bullet & \text{Formula: The absolute refractive index (\(n\)) is given by the formula: } \\ \bullet & \text{Properties:} \\ \bullet & \text{It is a dimensionless quantity as it is a ratio of two similar quantities.} \\ \bullet & \text{Since the speed of light is maximum in a vacuum, the absolute refractive index of any medium is always greater than or equal to 1. It is exactly 1 for a vacuum. } \\ \end{array}\]