More about WaveS 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. Music of the Spheres


Musical instruments are often based on plucked strings and the sound waves that were generated. Ancient Greeks attributed magical significance to the integer ratios that appear in a tuned harp, for example. That is, when the ratios between lengths of string were integer values (2, 1/2, 1/3, 2/3, 1/4), the harp was in tune, when it was not an integer ratio (e.g., 1/3.141529) it was out of tune. Can you find a more mundane (boring physics!) explanation for the fact that beautiful music is related to integers, than the ancient Greeks who attributed it to Celestial harmonies?




2. The Multiple Choice

The amplitudes and phase differences for three pairs of waves having the same wavelength are given in the table below. Each pair of waves travels in the same direction along the same string, only varying by phase. Without written calculation, rank the pairs according to the amplitude of the resultant wave, greatest first.
NumberAmplitude 1Amplitude 2Phase Difference
1 2mm 5mm Pi radians
2 7mm 9mm Pi radians
3 2mm 2mm 0 radians

1, 2, 3
3, 2, 1
3, 1, 2
2, 3, 1

3. Another Physlet


Find the frequency, period, and amplitude of the two waves, that when added together, produce a standing wave with 4 nodes, 3 antinodes, and a maximum displacement of 5 (units). That is, you must modify the equation of the two waves f,g in the boxes right below the animated wave. (When I get the bugs ironed out, the wave will be animated here, until then, scroll down to the bottom of the page.)





honors extra


A schoolyard game that was popular 100 years ago, was called "Crack the Whip" or "Snap the Whip". In this game, pictured above, a number of children would link hands and the leader would run a curving path that caused the last child in the chain to lose his grip. Why is it that no one else lost their grip? What is so special about being the last one in the chain? Does this have any similarities to the bullwhip problem on quiz zero?





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.



Standing Wave Demonstration

Superposition of Waves

f(x,t) =

g(x,t) =

Physlet Description

The animation above illustrates the sum of 2 traveling waves.  Position is in centimeters and time is in seconds. Place the cursor on the graph and left-click the mouse to get coordinate information.
[ReStart if totally confused.]

Credits

This physlet problem contributed by Randy Jones at Loyola College: email: RSJ@Loyola.edu