1.A sound wave in an unknown gas has a frequency of 461 Hz and a wavelength of 0
ID: 1304641 • Letter: 1
Question
1.A sound wave in an unknown gas has a frequency of 461 Hz and a wavelength of 0.7 m. What type of gas might it be? Hint: Use the table below.
2.Consider a sound wave of frequency f generated in air by a loudspeaker. When this sound wave reaches a nearby lake, the sound wave propagates into the water, where it has the same frequency f. What is the ratio of the wavelength of the wave in the water to the wavelength in air?
3.a.You are at a rock concert, and the sound intensity reaches levels as high as 100 dB. The sound pressure produces an oscillating force on your eardrum. Estimate the area of the ear drum. (answer in mm^2)
b.Calculate the amplitude of this oscillating force. (Use your estimate.)
4.A source of sound has a total emitted power of 215 W. What is the intensity a distance of 5 m from the source? Assume the source emits spherical waves.
Explanation / Answer
1) v = lambda f = 461*0.7=322.7 m/s so maybe oxygen gas
2)
lambda water = lamda air/n
n = 1.33
lambda water/lamda air = 1/1.33 = 0.752
3) a) radius ~ 1mm
A = pi 1^2 = 3.14 mm^2
b) F = P*A
100 = 10 log(I/I0)
I = 10^(-2) = P/A
P = 3.14E-6*10^-2 = 3.14E-8 N/m^2
F = PA = 0.86E-8 N
4) I = P/A =215/(4*pi*5^2)= 0.68
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