TPRH SW #303 - Increase in frequency mandates a decrease in wavelength, right?

[Trayshawn]

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Increase in frequency mandates a decrease in wavelength, right? So whats up with this TPRH question?

As the frequency of a wave is increased, which of the following must always decrease?
a) period
b) amplitude
c) wavelength
d) speed

answer is a. of course, period will decrease. but wavelength should as well. there isn't even a reference to this answer choice in the explanations. Is this just a bad question?

 

[sp808]

Increase in frequency mandates a decrease in wavelength, right? So whats up with this TPRH question?

As the frequency of a wave is increased, which of the following must always decrease?
a) period
b) amplitude
c) wavelength
d) speed

answer is a. of course, period will decrease. but wavelength should as well. there isn't even a reference to this answer choice in the explanations. Is this just a bad question?

You can increase wave speed and keep wavelength fixed.

 

[juneafternoon]

In that situation, wavelength will only decrease if you're trying to keep the speed of the wave constant. (speed = wavelength x frequency). Since that's not a condition stipulated in the question, the only decrease that you can say for certain will decrease is the period, as period = 1/frequency; inversely proportional.

 

[Postictal Raiden]

As a free-standing question, this one is poorly worded.

 

[Trayshawn]

In that situation, wavelength will only decrease if you're trying to keep the speed of the wave constant. (speed = wavelength x frequency). Since that's not a condition stipulated in the question, the only decrease that you can say for certain will decrease is the period, as period = 1/frequency; inversely proportional.

yea, but wave speed only changes with wavelength. Frequency always remains fixed throughout wave speed changes. So, from purely mathematical considerations, wavelength does not have to increase, but from a physical standpoint, it must. right?

 

[polyatomic]

No matter what, just go for the "best answer"

Wavelength could change, but you know period HAS to change without a doubt, since there are no other factors in the relationship between frequency and period f = 1/T

Wavelength can change in some situations, but there are always other variables working with wavelength and frequency.

I find I do this a lot in questions...where I absolutely know one answer is correct, then I see another answer that "might" work as well. For these questions, just always go with what you absolutely know, no matter how poorly worded a question is.

 

[sazerac]

As a free-standing question, this one is poorly worded.

As a free standing question, it is beautifully worded. It doesn't ask what "can" decrease, it asks what "must" decrease. It would be very easy to bring in a lot of outside information and get the question wrong. It would be very easy to bring in some outside assumptions and get it wrong.

The MCAT punishes people who do either of those strategies, and rewards those who simply answer the question and move on. At the heart of it all, this is a very very simple question, yet it separates those who sort of know what is going on from those who really know what is going on.

 

[LoLCareerGoals]

Yep. No one said it was an electromagnetic wave with a fixed speed of c or an audio wave etc. Looks fine to me. Waves are mathematical abstractions first and descriptors of natural phenomena in special cases.

 

[juneafternoon]

As a free standing question, it is beautifully worded. It doesn't ask what "can" decrease, it asks what "must" decrease. It would be very easy to bring in a lot of outside information and get the question wrong. It would be very easy to bring in some outside assumptions and get it wrong.

The MCAT punishes people who do either of those strategies, and rewards those who simply answer the question and move on. At the heart of it all, this is a very very simple question, yet it separates those who sort of know what is going on from those who really know what is going on.

This.