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Q91

Q91

Postby SeoM » Sun Apr 12, 2020 5:56 am

" A particular sound wave in air has a pitch of 3500 Hz and a wavelength of 17 m. It then travels through water where it moves four times as quickly as it does in air. What is the ratio of the wavelength of the wave in air to its wavelength in water?"

For this question I understood it to mean ... air wavelength: water wavelength, because of the last sentence ... which would be 4:1 not 1:4, wouldn't it?

Sorry if this seems silly!
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Re: Q91

Postby goldstanda3269 » Mon Apr 13, 2020 2:36 pm

SeoM wrote: I understood it to mean ... air wavelength: water wavelength, because of the last sentence ...


Correct.


SeoM wrote:
... which would be 4:1 not 1:4, wouldn't it?


The opposite!

In water, the wave has 4 times the velocity, so using velocity = frequency x wavelength where the frequency is constant, water must have 4 times the wavelength. And, since you have already agreed that water is 2nd in the ratio, then 1:4 indicates that water is 4x the original value.
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