Dimensional formula of refractive index

How to derive it

Refractive index = Speed of light in vacuum ÷ Speed of light in the medium

Put in the dimensions of each part: [LT⁻¹] ÷ [LT⁻¹] = [M⁰ L⁰ T⁰].

mass (M)

0

length (L)

0

time (T)

0

current (A)

0

temperature (K)

0

SI unit

The SI unit of refractive index is no unit.

Same dimensions as refractive index

These quantities have exactly the same dimensions, a favourite trick in JEE and NEET "which pair has the same dimensions" questions:

• Strain
• Coefficient of friction
• Poisson's ratio
• Relative density

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