Physics Demo Number: 069
Approximate Run Time: 5 min
Detailed Electronic Display of Amplified Sound Wave to Show Doppler Shifts
Demo Description
One may hook a microphone up to the sound-in jack of the lecture hall PC and watch the output of
the mike in the program Spectrum Lab on the computer .
Use one of the 'singing' Al rods as the sound source.
Then moving the rod quickly toward the mike will be seen to slightly
increase the frequency of the sound signal being received by the mike.
Similarly, pulling the rod quickly away from the mike causes the received frequency to be decreased
slightly.
Scientific Principles
-
Doppler shifts of sound signals moving relative to a stationary detector.
Equipment & Set Up
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Microphone secured to the end of a rod with a connecting electrical cable that can be plugged into the sound-in jack of the lecture hall PC.
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Software Program named Spectrum Lab installed on the computer.
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1.5 M Al rod with its end-to-end center marked with an inscribed circular scratch.
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Block of Violin Bow Resin to Coat the rod and allow one's sliding fingers along the length to excite a standing longitudinal wave in the rod , while holding the center point of the rod firmly between two fingers of the non -resined hand.
