Physics4BL 4

# Physics4BL 4 - B r ian Sek Physics 4BL Lab 7 Lab Partner...

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Brian Sek May 21, 2009 Physics 4BL, Lab 7 Lab Partner: Morgan Fryar Speed of Sound and Light Introduction The purpose of this lab is to measure the speed of sound and electromagnetic waves using a speaker and microphone. The first part of the experiment is to measure the wavelength and the wave propagation of sound waves at different frequencies. The objective next part was to measure the length of standing waves with a speaker, microphone, and moving reflector. In the last part of the experiment, standing electromagnetic waves were measured using a cordless phone and a moving reflector. Experimental Results Part 1: Travelling Sound Waves A loudspeaker produces sound waves and a microphone is used to detect them. The speaker is connected to a function generator. A connector sends the signal from the generator to the speaker and the oscilloscope. CH1 displays the function generator’s signal, while CH2 displays the microphone’s. Measurements are taken at distances that 2 π , 4 π , and 6 π of the frequency. This is done at five different frequencies. Using the frequency and the changes in distance, the dispersion relation of the wave is calculated using the equation ω = λ fk, with λ f being the velocity of the wave. Table 1: Frequency (Hz) Wavelength (m) Phase Velocity (m/s) 3500 0.1027 359.33 7000 0.0504 378.00 10500 0.0360 378.00 14000 0.0263 368.67

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17500 0.0210 367.50 This table shows the phase velocity, which is calculated by multiplying the frequency by the wavelength. Part 2: Standing Sound Waves Like the first part of the experiment, the microphone and the speaker are used. However, this time, a moving reflector will be used to reflect the sound waves back, to create standing waves. The first task is to calibrate the position of the reflector. A ruler is used to measure the distance that the reflector travels, while the voltage is being measured. Ten points,
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Physics4BL 4 - B r ian Sek Physics 4BL Lab 7 Lab Partner...

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