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  4. A student when discussing the properties of. a medium (except vacuum) writes Velocity of light in vacuum = Velocity of light in medium This formula is

Q. A student when discussing the properties of. a medium (except vacuum) writes Velocity of light in vacuum = Velocity of light in medium This formula is

Physical World, Units and Measurements Report Error

Solution:

The formula can be written as
$\frac{\text { Velocity of light in vacuum }}{\text { Velocity of light in medium }}=1$
This formula is dimensionally correct as both the sides are dimensionless. Numerically, this ratio is equal to refractive index which is greater than $1$.
Hence, the equation is numerically incorrect.

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