Question

Minimum and maximum refractive index of which medium has

Answer 1

For amplitude modulation, the maximum and minimum values of modulation index are 1 and 0. You can have it above 1, but you cannot recover the signal at the receiver and it is of no use. This phenomenon is called as over modulation. Modulation index is always positive so cannot be less than 0.

Sometimes, modulation index is expressed as a percentage of carrier amplitude, which is more intuitive to understand the max and min values.

Definition of modulation index varies for amplitude, frequency and phase modulation. I described about amplitude modulation, it may differ for other types of modulation