Question

The unit for refractive index is

• A. m/s
• B. m/s\(^2\)
• C. kg/m\(^3\)
• D. No units

Hint:

Refractive index: \[ \boxed{n=\frac{c}{v}} \] Since it is the ratio of two speeds, it is a dimensionless quantity and has no unit.

Answer 1

The Correct Option is D

Concept: The refractive index of a medium is defined as \[ \boxed{n=\frac{c}{v}} \] where
• \(c\) = speed of light in vacuum,
• \(v\) = speed of light in the medium.

Step 1: Substitute the units.
Both \(c\) and \(v\) have the same unit, \[ \text{m/s}. \] Therefore, \[ n=\frac{\text{m/s}}{\text{m/s}}=1. \]

Step 2: Interpret the result.
Since the units cancel each other, \[ \boxed{\text{Refractive index is a dimensionless quantity.}} \] Hence, it has no unit.

Step 3: Final conclusion.
Therefore, the correct answer is \[ \boxed{\text{No units}.} \]