EK FL1: Echolocation

[FCMike11]

Question #40 of the Chemical and Physical Foundations of Biological Systems Section

Question states:
"Suppose each click emitted by a human echolocator represents one wavelength. If the speed of sound in air is 343 m/s, what is the wavelength of the sound waves that are produced?"

In the paragraph it gives you this information: "The echolocation click produced by such individuals tends to be short (approximately 10 ms) and spectrally broad."

I mistook the information of 10 milliseconds to be the frequency. Which gave me an answer listed; but I should have understood that this is the period (looking at the solution). Should I have known this since the units were not Hz? The wording is really strange to me...and i've not seen that description previously associated with the period (I know frequency = 1/t & v =wavelength * frequency); just got tripped up.

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[NextStepTutor_3]

Good question! In general, you're on the right track - units give us a major hint here, as a frequency value would typically be given in Hz. Specifically, though, it's important to know what 1 Hz refers to. Hertz (the SI unit for frequency) are equivalent to cycles / s (you can even think of them as "wavelengths per second" in this context). In SI base units, Hz are equivalent to s^-1 (in other words, "1 / seconds").

Now that we know that frequency can be given as s^-1, we can be confident that a value given in seconds is NOT a frequency value, and probably refers to the period. After all, f = 1 / period, and s^-1 = 1 / s. From here, we can simply take the reciprocal of 10 ms to find frequency.

 

[aldol16]

Always use unit analysis. Your units must come out to be the same on both sides of the equation or the equality does not hold. Therefore, m/s must equal m/s and from that, you know that your frequency must be in units of 1/s.

 

[FCMike11]

Always use unit analysis. Your units must come out to be the same on both sides of the equation or the equality does not hold. Therefore, m/s must equal m/s and from that, you know that your frequency must be in units of 1/s.

Ok gotcha. Basically, you are multiply (m/s) * s^-1 which will = m (units if wavelength). Missing a large proportion of my problems by details like this instead of gaps of knowledge; they definitely take advantage of this, too.

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