Sound waveS II PREFLIGHT

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The following three questions refer to the material you were to read in preparation for the lesson. Questions one and three require you to write a three or four sentence response. Number two is a multiple choice question. Click in the appropriate circle.

You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button at the bottom of this page. Don't submit more than once. (If you absolutely HAVE to resubmit it, put a note on the end to that effect.)




1.

During my exceedingly arduous move to Huntsville (cspar181.uah.edu/RbS/trip.txt), I purchased 2 CB radios for the moving van and my car, so as to avoid being separated from my wife. They came with a 3 foot antenna that attached with a magnet to the roof of my car. I noticed that truckers had similar antennae attached to BOTH their left and right rearview mirrors, forming a pair. If the wavelength of radio waves is roughly 2 to 4 times the length of the antenna (which is explained in an advanced course in electrical engineering), what will be the effect of having two antennas on both sides of the truck? That is, why do the truckers do this? (You can test out your theories with a previous Physlet.)




2.

Doppler Demonstration

The animation represents a cross section of a three dimensional sound wave propagating away from a moving source.  In which of the animation(s) is the source traveling slower than the speed of sound?

Animation 1  Animation 2  Animation 3  Animation 4  Animation 5 


Animations 1, 2 and 3

Animations 1 and 2

Animations 4 and 5

Insufficient information. (Explain below.)


3.


In problem 2, we showed a moving source emitting sound waves. Using Animation 5, calculate the speed of the source in units of the sound speed, e.g., Mach units. Explain what method you used to do this calculation.




honors extra


In Huntsville, tornadoes are big business. I'm told that the TV stations have better radar units than the Weather Service. So rather than listen to the weather radio, everyone tells me to turn on the local TV weather station. Evidently, the TV guys are so proud of their radar, they advertise "Doppler Max", as part of their name. Just what is this big thing about Doppler? How is it related to tornadoes? If a tornado has a wind speed of 300 miles per hour, and the radar has a frequency of 4 GHz, just how much Doppler are we talking about?






Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):




You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button.

I received no help from anyone on this assignment.