Waves crash onto a beach every 41 s. What is their frequency? Answer in units of

Question

Waves crash onto a beach every 41 s. What is their frequency? Answer in units of Hz. The sound level produced by one singer is 74.5 dB. What would be the sound level produced by a chorus of 27 such singers (all singing at the same intensity at approximately the same distance as the original singer)? Answer in units dB. What is the period that corresponds to a frequency of 58.3 Hz? Answer in units of s A violin string playing the note "A" oscillates at 440 Hz. what is the period of the string's oscillation? Answer in units of s

Explanation / Answer

15)  if 14 waves crash every 41 sec
then 1 wave crashes every 41sec/14 = 2.93s
2.93s is the "period" of one wave.

frequency = 1/period
that means the frequency is 1 cycle /2.93 s = 0.341 cycles/s = 0.341 Hz

16) The intensity of each singer is 74.5dB = 10dB*log(I/10^-12) So I = 10^7.45*10^-12 = 2.82x10^-5W/m^2
So 27 singers would produce 27*2.82x10^-5 = 7.614x10^-4 W/m^2
So on the dB scale beta = 10dB*log(7.614x10^-4/10^-12) = 88.82 dB

17) Period = 1/frequency = 1/58.3 = 0.01715 s

18) Period = 1/frequency = 1/440 = 2.27 ms

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