Detection of sounds tbr packet

[dahmsom]

Why is the answer B?
If the strings have the same length which is 12 inches . Which is 1/3 of a meter then 2/3 of a wavelength is to be measured of the standing waves . I'm confused on how they got to this explanation . Can someone please clarify ??!

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[OrdinaryDO]

Can you show the whole question?

 

[dahmsom]

The question is number 13 oops . And the info is needed on top . The paragraph cut out isn't really needed

 

[OrdinaryDO]

Well, I am not sure if this helps, but I would have chosen B due to the face that L = wave length/2. (0.3m = (W.L.) / 2.....= 0.6m) which is closest to the answer choice B. What does the explanation say?

 

[BerkReviewTeach]

Ah yes, passages from the class handouts. I'd strongly recommend you go to Todd's office hours for help on this, but in case you can't make it to his, here goes.

For a stringed instrument like the violin, each string produces a different resonant frequency. The equation for frequency on the string is ƒn = nv/2L. So the difference in frequency between each string can be attributed to either (1) a different natural wave speed on each string or (2) a different string length for each string. You either need to know that the frequencies are different because of different speeds (caused by different thicknesses for each string) or you need to read from the passage "The four strings of a violin all have the same length of rough twelve inches." The harmonic wavelengths for a standing wave are 2L/n, where the fundamental wavelength has an n of 1. This is because half of the wave extends from one node (one end of the string) to the other node (the other end of the string). To get a full wave (fundamental wavelength), you need to double the length of the string, which is why lambda1 = 2L. 2 x 0.326 = 0.652.

 

[dahmsom]

Wow thanks @BerkReviewTeach . this was a great explanation . So if wavelength = 2L/n. Given that 12 inches is the same for all strings.. i had to convert it to meters i think i made a mistake there but it should be around B. I took the berkeley review last year, so i cant make it to todds office hour. But hopefully i can ask you questions since im using the TBR for physics and chemistry .

 

[dahmsom]

Well, I am not sure if this helps, but I would have chosen B due to the face that L = wave length/2. (0.3m = (W.L.) / 2.....= 0.6m) which is closest to the answer choice B. What does the explanation say?

"the standing wave is associated with the fundamental frequency of the strings. There are no nodes between the endpoints of the strings in the the fundamental mode, so the string is half a wavelength long. this means that the wavelength is twice the length of the string. the wavelength is the same for all four of the strings, since all the strings have the same lengths. The passage state that the strings are about 12 inches in lengths, which is 1/3 of a meter. this means that the wavelength is roughly 2/3 of a meter."

 

[OrdinaryDO]

"the standing wave is associated with the fundamental frequency of the strings. There are no nodes between the endpoints of the strings in the the fundamental mode, so the string is half a wavelength long. this means that the wavelength is twice the length of the string. the wavelength is the same for all four of the strings, since all the strings have the same lengths. The passage state that the strings are about 12 inches in lengths, which is 1/3 of a meter. this means that the wavelength is roughly 2/3 of a meter."

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[dahmsom]

Lol @OrdinaryMD thanks for the help tho. I understand it -_-. haha i really brain farted.