AAMC 4 CBT - PS Question 11

[thomasfx10]

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I must be having a brain freeze or something ... I might have over thought this one out

The question has four graphs (y- Speed, X-Change in wavelength) asking which graph best represents the speed of the transmitter away from the receiver and the increase in wavelength of the signal.

Table 1

Speed ... Change in Wavelength 10^-5m

246 12
322 16
447 22
etc ...

The correct answer was a linear graph in a positive direction. That was NOT my answer choice.


My question ... if the wavelength is going from 12x10^-5m to 16x10^-5m as the speed increases is not the wavelength getting smaller as in more negative?

I am tired and might not be thinking straight ... thanks for any comments

 

[btc8]

I must be having a brain freeze or something ... I might have over thought this one out

The question has four graphs (y- Speed, X-Change in wavelength) asking which graph best represents the speed of the transmitter away from the receiver and the increase in wavelength of the signal.

Table 1

Speed ... Change in Wavelength 10^-5m

246 12
322 16
447 22
etc ...

The correct answer was a linear graph in a positive direction. That was NOT my answer choice.


My question ... if the wavelength is going from 12x10^-5m to 16x10^-5m as the speed increases is not the wavelength getting smaller as in more negative?

I am tired and might not be thinking straight ... thanks for any comments

As the sound moves away from the observer, the frequency and pitch decrease. Since v=f*lamba, and v is constant for sound, decrease f and you increase the wavelength. In the example, the wavelength is getting progressively longer.

I always think in terms of frequency and use the v=f*lamba equation.

 

[thomasfx10]

So just so I am square on this ...

16x10^-5m <== This is a larger wavelength

12x10^-5m <== Than this ???

12X10^-4m <== and this ???

I thought the more neg. you went the smaller things are ... I am tired ..

Thanks

 

[btc8]

So just so I am square on this ...

16x10^-5m <== This is a larger wavelength

12x10^-5m <== Than this ???

12X10^-4m <== and this ???

I thought the more neg. you went the smaller things are ... I am tired ..

Thanks

The one you pointed out is SMALLER/SHORTER. 12x10^-4 is the LONGEST wavelength because its number is largest.

 

[thomasfx10]

Thanks for clearing that up. That is what I thought.

So back to the question then ... So if the speed is increasing then the wavelength is getting longer?

The chart is showing wavelength getting smaller as speed increases. Am I reading the table correct?

Table 1
Speed ... Change in Wavelength 10^-5m
246 .............12
322 .............16
447............. 22

 

[btc8]

Thanks for clearing that up. That is what I thought.

So back to the question then ... So if the speed is increasing then the wavelength is getting longer?

The chart is showing wavelength getting smaller as speed increases. Am I reading the table correct?

Table 1
Speed ... Change in Wavelength 10^-5m
246 .............12
322 .............16
447............. 22

Yes. As the object moves away, notice how the change in wavelength is larger. This means that there is a larger (relative) change in wavelength from the the original--in this case, larger=longer wavelength.

So, since the object is moving away, the frequency decreases, and the wavelength increases.

 

[thomasfx10]

Relative! That is what I was look for ...

So in summary ... Even though

16x10^-5m is a smaller wavelength than 12x10^-5m

The table is showing an increase relative to the other values ... I hope that is correct!

Thanks

 

[Axon hillock]

16x10^-5m is a larger wavelength than 12x10^-5m

Edit: I think your letting the negative thing confuse you. It's not a negative number, it's just a fraction. Write it out the long way to see which is larger

 

[thomasfx10]

Yes! I see the light!

That is exactly what I was doing ...

.0000016 Larger

.0000012

Thanks!