Three waves of equal frequency having amplitudes 10 μm, 4 μm and 7 μm arrive at a given point with successive phase difference of π2. The amplitude of the resulting wave in μm is given by

The wave 1 and 3 reach out of phase. Hence resultant  phase difference between them is π.∴ Resultant amplitude of 1 and 3 = 10−7=3μmThis wave has phase difference of π2 with 4μm∴ Resultant amplitude = 32+42=5  μm