Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Physics Problem (with frequency)

  1. Jan 25, 2005 #1
    A sound wave has a frequency of 700 Hz in air and a wavelength of .50m. What is the temperature of the air?

    speed of sound in air = 345 m/s.

    I dont even get how to go about this problem....i dont know the equation
  2. jcsd
  3. Jan 25, 2005 #2
    I believe the mistake you made was to assume that the spped of sound in air is 345 m/s. You can tell just based on the information you are given in the question. If the frequency is 700 Hz and the wavelength is 0.5 m, then what MUST the speed of sound be?

    There is actually a formula that relates speed of sound in air with temperature. Find that and you shall find the answer you desire.
  4. Jan 25, 2005 #3
    Yupp, remember when the air molecules are heated up, it moves faster.
  5. Jan 25, 2005 #4
    [tex]v\approx 331\mbox{m/s}+0.6\mbox{T}[/tex]

    where [itex]v[/itex] is the speed of sound in air, and [itex]\mbox{T}[/itex] is the temperature in degrees Celsius.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook