Question

Three waves of equal frequencies having amplitudes $10\mu m$, $4\mu m$ and $7\mu m$ arrive at a given point with successive phase difference of $\pi /2$. The amplitude of the resulting wave (in $\mu m)$ is given by-

Answer 1

As three waves are at successive phase difference of $\pi /2$ from each other,
The resultant amplitude of first and third wave is $=10-7=3\mu m$
This wave now has a phase difference of $\pi /2$ with second wave of amplitude $4\mu m$
Hence resultant amplitude-
$a=\sqrt{(3{)}^2+(4{)}^2}=5\mu m$.