Three waves of equal frequency having amplitudes `10mum`, `4mum`, `7mum` arrive at a given point with successive phase difference of `pi//2`, the amplitude of the resulting wave in `mum` is given by

Options

A. `7 mu m`
B. `6mu m`
C. `5 mum`
D. `4 mu m`

Answer

C

Explanation

For the first and third wave, the phase difference = `pi`
Their resultant amplitude `= 10 - 7 = 3mu m`
This has a phase difference of `pi//2` with the second wave
`:. R = sqrt(3^(2) + 4^(2)) = 5mu m`