Homework Help: physics

Posted by Sandhya on Sunday, November 9, 2008 at 5:29am.

1) Sound propagating through air at 30 degree Celsius passes through a vertical cold front into air that is 40 degree Celsius. If the sound has a frequency of 2400 Hz, by what percentage does its wavelength change in crossing the boundary?

(2) What is the intensity of a sound that has intensity level of (a) 50 dB or (b) 90 dB?

physics - drwls, Sunday, November 9, 2008 at 6:38am
(1) The sound speed increases in proportion to the square root of the absolute temperature change, sqrt (313/303) = 1.016. That is a 1.6% increase in sound speed and will result in a 1.6% increase in wavelength, since
wavelength = (sound speed)/(frequency)

2. Use the table at http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/sound/u11l2b.html
to find your answer
physics - Sandhya, Monday, November 10, 2008 at 5:19am
Thanks for your easy solution for prob1
By the way is it not 1.016% ?
I solved prob 2 using the formula
Intensity level L = 10 log(I / I0) where I0 = 10^-12 watt/sq.m

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