AAMC 3 Passage 4 on Harmonics

[an aspiring doctor]

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This question is for those who have done this exam. In passage 4 there is a graph with three different harmonics and you are asked various questions on them that all involve their order. How do you know which harmonic is number 1,2, etc.? Is there a way of deciphering them from the solid and dashed lines?

 

[brood910]

Know the relationship between n and wavelength.

 

[8player]

This question is for those who have done this exam. In passage 4 there is a graph with three different harmonics and you are asked various questions on them that all involve their order. How do you know which harmonic is number 1,2, etc.? Is there a way of deciphering them from the solid and dashed lines?

Did you ever figure this out?

 

[aldol16]

Did you ever figure this out?

I'm assuming you're reviving an old thread because you have the same question? The answer is that if you have a tube, more wavelengths fit inside with higher harmonics. In other words, the frequency increases and wavelength decreases.

 

[8player]

I'm assuming you're reviving an old thread because you have the same question? The answer is that if you have a tube, more wavelengths fit inside with higher harmonics. In other words, the frequency increases and wavelength decreases.

Well in the passage question, we're just given a graph with 3 different waves shown and told that the graph shows the 1st three harmonics. That's all the info we're given. So how do you know which one came first?

 

[aldol16]

Well in the passage question, we're just given a graph with 3 different waves shown and told that the graph shows the 1st three harmonics. That's all the info we're given. So how do you know which one came first?

There's no particular order to harmonics. The only thing governing a harmonic is the wavelength or frequency. The first harmonic always has some definite wavelength that is larger than the second harmonic that is larger than the third harmonic, etc.

 

[NextStepTutor_3]

Yes - the first harmonic is represented by the wave with the largest wavelength and smallest frequency. That's why you'll often see "first harmonic" used interchangeably with the term "fundamental frequency" - the lowest resonant frequency possible with regard to that particular situation. The second harmonic always has a shorter wavelength (and larger frequency), while the wavelength of the third harmonic is even shorter, and so on.

If this is confusing, it's not a bad idea to review open and closed pipes. The passage you referred to doesn't deal with a pipe specifically, but you might notice that the fundamental frequency has a wavelength exactly twice as long as the second harmonic and three times as long as the third. This is a similar situation to what you'd find in the case of an open pipe.

Good luck!