# Modulation index of FM

## The modulation index of FM is given by

**Options:**

μ = frequency deviation/ modulating frequency

μ = modulating frequency /frequency deviation

μ = modulating frequency/ carrier frequency

μ = carrier frequency / modulating frequency

Correct Answer: μ = frequency deviation/ modulating frequency

**Explanation: **

Modulation index is the measure of how much the modulation parameter changes from its un modulated value.The modulation index of FM is given by

μ = frequency deviation/ modulating frequency

= Δf/ f_{m}

Where Δf is the peak frequency deviation i.e. the deviation in the instantaneous value of the frequency with modulating signal.

f_{m} is the value of modulating frequency