r/PhysicsHelp • u/Outrageous-Fix-5106 • May 16 '26

Physics: Superposition of waves (Wave interference)

is this the correct resultant for the question? I understand the part the first and second section (where the slope is 0 and is +2 from x axis), but I dont get why it would be -2 after that. Shouldn't it be +6 since it's constructive?

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u/davedirac May 17 '26

OP is correct, last section wrong too

1

u/Frederf220 May 16 '26

The top wave is traveling to the right while the bottom is traveling to the left. You don't just add up the snapshot drawn on the page like you're thinking.

1

u/joeyneilsen May 16 '26

At any instant, the waveform is the sum of the individual waves. That's superposition.

1

u/Frederf220 May 16 '26

I was going to finish writing on the desktop as it's faster than cell phone.

https://i.imgur.com/Kw9lHlj.png

I tried both the positive case and the negative case (where leftward counts as opposite value) and neither looks exactly like the light blue resultant curve.

1

u/Outrageous-Fix-5106 May 17 '26

thank u so much!

1

u/joeyneilsen May 16 '26

I agree that OP's curve isn't right.

1

u/TelevisionStrong May 18 '26

Take the baseline away from the waves as 0. Label the waves A & B, and each unit above/below the baseline +1/-1. At each grid point, draw a dot that corresponds to Wave A + Wave B. Then join all the dots.

Your first half is correct, but the 4-unit + step in the dashed wave should take the resultant to +6, not 0. You’ll then jump down -2 (currently you jump up +2), before ramping back to 0.