Give noticeable points about the amplitude of resultant waves of two harmonic progressive waves on a stretched string.

(N/A) The amplitude of the resultant wave is a function of the phase difference $\phi$ between the two component waves.
The resultant amplitude $A$ is given by the formula: $A(\phi) = 2a \cos(\frac{\phi}{2})$,where $a$ is the amplitude of each individual wave.
$1$. When the two waves are in phase,the phase difference is $\phi = 0$. Substituting this into the formula,we get $A = 2a \cos(0) = 2a$. This is the maximum possible amplitude,known as constructive interference.
$2$. When the two waves are completely out of phase,the phase difference is $\phi = \pi$. Substituting this into the formula,we get $A = 2a \cos(\frac{\pi}{2}) = 0$. This results in zero amplitude,known as destructive interference.
$3$. For any other phase difference,the resultant amplitude $A$ will lie in the range $0 \leq A \leq 2a$.