Question

A student when discussing the properties of a medium ( except vaccum) writes
Velocity of light in vaccum = Velocity of light in medium
This formula is
A. Dimensionally correct
B. Dimensionally incorrect
C. Numerically incorrect
D. Both `a and c`

Answer 1

Correct Answer - D
The formula can be written as
`("Velocity of light in vaccum") /("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.