Three waves of equal frequency having amplitudes $10 \,\mu \, m, 4 \, \mu \,m$ and $7 \mu m$ arrive at a given point with successive phase difference of $\frac{\pi }{2}$. The amplitude of the resulting wave in $\mu \,m$ is given by
A$7$
B$6$
C$5$
D$4$
AIIMS 1995, Medium
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C$5$
c (c) The wave $1$ and $3$ reach out of phase. Hence resultant phase difference between them is $\pi $.
$\therefore $ Resultant amplitude of $1$ and $3 = 10 - 7 = 3 \mu m$
This wave has phase difference of $\frac{\pi }{2}$ with $4 \mu m$
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