# Physics: wavelength of sound waves

## Homework Statement

Stated in the attached file.

## Homework Equations

Wavelength = 2 times length divided by harmonic
I don’t know if it’s the relevant equation

## The Attempt at a Solution

I used the equation I wrote. So, if the left side is 10cm longer, I guess it might be 2(10).

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mfb
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20 cm is right, but I'm not sure you used the right formula.
10 cm corresponds to one of 1/2, 3/2, 5/2, ... times the wavelength, only the first option leads to a possible answer.

I used this formula, is it the right one?

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mfb
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No. That looks like something for constructive interference.

20 cm is right, but I'm not sure you used the right formula.
10 cm corresponds to one of 1/2, 3/2, 5/2, ... times the wavelength, only the first option leads to a possible answer.
I think that’s the same rule. If wavelength=2*length / n, where n can be 1,2,3,4,5,6,...(the one wrote in the picture)
It’s basically the same as you said but solving for length not wavelength. I mean, length =1/2 *n*wavelength.
Right?

mfb
Mentor
For destructive interference you want the length difference to be (n+1/2) wavelengths where n is an integer: L = (n+1/2)λ or 2L = (2n+1)λ or ##\lambda = \frac{2L}{2n+1}##. Your formula works if you require n in it to be odd.

I am confused now. That’s a little bit different from I have learned. Or is this rule for these type of questions?

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mfb
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You do not have a standing wave here. You have two waves from different tubes interfering.

YMMMA
You do not have a standing wave here. You have two waves from different tubes interfering.
Yes, okay then. Thanks!