# Homework Help: Wave constructive and/or destructive interference question

1. Oct 16, 2014

### kirsten_2009

1. The problem statement, all variables and given/known data
https://portal.utoronto.ca/courses/1/Fall-2014-PHY100H5-F-LEC0101/ppg/quiz%2061016132114/f1q2g1.jpg

The figure shows two sets of water waves, created by two sources labeled "A" and "B." The solid half-circles represent wave crests from A, and the dashed half-circles represent wave crests from B. Suppose that individual wave crests from either source A or source B alone are 5 mm above the level of the undisturbed water. Then the displacement of the water [above or below the level of the undisturbed water] at the point marked "x" [with the arrow pointing toward it] is

A.) -10 mm.
B.) 0 mm.
C.) +5 mm.
D.) +10 mm.
E.) -5 mm.

2. Relevant equations

N/A

3. The attempt at a solution
I think it would be E.) -5mm because if we are just taking one wave set alone (either A or B) then there would be no interference from the other wave set and if the displacement from rest is 5mm then the opposite displacement must be equal in magnitude...? But I don't actually know...I'm just thinking it out....would you please correct me if I'm wrong? Thanks in advance!

2. Oct 16, 2014

### RUber

I cannot see your figure. Could you check to see that it was attached properly?

3. Oct 16, 2014

### RUber

Although I cannot see the picture, here is a hint. You can add the wave effects together. So, if x lies on a wave crest from A, (+5mm), and the midpoint between crests from B (-5mm), then the total displacement at x would be 0.

4. Oct 20, 2014

### kirsten_2009

Hello,

Yes, unfortunately there was no way to upload the image but thank you for your help...it actually helped me get the answer! :)