Resultant Intensity of Water-waves

[HSTay]

Homework Statement

Two wave generators S1 and S2 produce water-waves of wavelength 4m. They are placed 4m apart in a water tank and a detector P is placed on the water surface 3 m from S1. (90 degree to S1S2, S2 to P is 5m)

When operted alone, S1 and S2 produce waves with intensity I and 3I at P respectively. When the generators are operating together and in phase, what is the resultant intensity at P?

Homework Equations

The Attempt at a Solution

A. 0.5I B. 2.0I C. 4.0I D 7.5I

 

[Doc Al]

Well, what do you think? Hint: Are the waves at P in phase, out of phase, or what?