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: Interference - Q done, is it right?

  1. Aug 1, 2012 #1
    Hi all, I have a question here that I've done but it hasn't got an answer provided. I'm sure it's easy stuff but haven't looked at this material in a while so
    just want to double check.

    (The things in red are what I added to the original diagram)

    intereferenceexampleQ.jpg

    RE-DONE

    d = √17

    d + λ/2 = 2√5

    λ/2 = 2√5 -d

    λ = 4√5 -2(√17)

    λ = 0.698m

    Using v=fλ

    ∴f = 340/0.698 = 487 Hz

    Is this correct?

    Thanks in advance
     
    Last edited: Aug 1, 2012
  2. jcsd
  3. Aug 1, 2012 #2
    [itex]d=\sqrt{1^2+4^2}=\sqrt{17}[/itex]
     
  4. Aug 1, 2012 #3
    Woops, muppet at work. No idea how that came about, thanks.

    Looking over it I've done a couple of very stupid errors such as line 4.

    First post RE-DONE
     
    Last edited: Aug 1, 2012
  5. Aug 1, 2012 #4
    Correct, but you get more frequencies:

    [itex](2n-1)\frac{\lambda}{2}=d\Rightarrow f=(2n-1)\frac{v}{2d},\,n=1,2,3,...[/itex]
     
  6. Aug 1, 2012 #5
    Thanks a lot, big help
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook