Maximum amplitude of message signal in amplitude modulation is $20 \mathrm{~cm}$. If the amplitude of carrier wave is $40 \mathrm{~cm}$, then modulation index of modulated wave is

The modulation index $\mu$ for an amplitude modulated wave is defined as the ratio of the amplitude of the message signal $A_m$ to the amplitude of the carrier wave $A_c$.

Given values are $A_m = 20 \text{ cm}$ and $A_c = 40 \text{ cm}$.

The formula for the modulation index is $\mu = \dfrac{A_m}{A_c}$.

Substituting the given values:

$\mu = \dfrac{20}{40} = 0.5$.

Answer: 0.5