Path length differences/ interference problem

[YMMMA]

Homework Statement

In the figure below, Two wave sources, M and N, are vibrating in phase on the surface of water and generate waves of wavelength λ. Which of the following values for the distances MP and NP will result in minimum disturbance at a particular point P on the surface of the water?

MP NP
I 5λ 5λ
II 5λ 6λ
III 5λ 6.5λ

Homework Equations

ΔL= mλ
ΔL= (m+½)λ

Where L is path length and m is an integer.

The Attempt at a Solution

[/B]I am not really sure if minimum disturbance means arriving out of phase (destructive interference).
If so, then the only possible answer is III. ΔL=1.5λ. Is that correct?

 

[Doc Al]

I am not really sure if minimum disturbance means arriving out of phase (destructive interference).
If so, then the only possible answer is III. ΔL=1.5λ. Is that correct?

Yes, sounds good to me. Minimum disturbance means the lowest amplitude of a wave at that point, which would be when they destructively interfere.