Explain why the wave shape is flat (zero displacement) at t = T/4 and 3T/4 in the figure. Why is it the negative of its original shape at t = T/2?
A complex
wave vanishes at a particular point in space at a certain time either
because a) all of its sinusoidal components vanish there at that time,
or b) because some of the various components that
are positive at that point and time cancel those that are negative at
that point and time. In the case of the wave vanishing everywhere at
say Similarly
after An
entirely different approach is possible: One can think of the standing
square wave as made up of two traveling square waves, one moving to
the right and the other moving to the left. (Indeed the animation
in this web site was made by using this idea.) The two waves have half
the amplitude of the total standing wave; when they are in phase they
add and the standing wave is its original shape or its negative; when
they slide 180
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What is the repeat time of a complex wave made up by adding together three sinusoidal waves having frequencies 18 Hz, 24 Hz, and 60 Hz?
The largest common factor of the three numbers 18, 24, and 60 is 6 (18 = 3x6, 24 = 4x6, 60 = 10x6). So the repeat frequency is 6 Hz and the repeat time is 1/6 s.
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A wave having the frequency spectrum shown is passed through a filter that removes all waves below 51 Hz. What is the repeat frequency of the resulting complex wave?
After
the filter acts, the frequencies remaining are the 60, 100, and 140
Hz components. The
____________________________________ The figure shows a pressure-time graph of a repetitive traveling sound wave. Which of the accompanying plots is the most likely frequency spectrum for this wave?
c)
The wave is repeating and thus requires a discrete spectrum. Answers
d) is continuous and so |

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