1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Wave Interference Question

  1. Oct 2, 2009 #1
    1. The problem statement, all variables and given/known data

    A two-point source operates at a frequency of 1.0 Hz to produce an interference pattern in a ripple tank. The sources are 2.5 cm apart and the wavelength of the waves is 1.2 cm.

    Calculate the angles at which the nodal lines in the pattern are far from the sources. (Assume the angles are measured from the central line of the pattern).

    Relevant equations:
    dsinO = (n-1/2)(wavelength)

    O = angle theta

    3. The attempt at a solution

    my problem is that i can't figure out how many nodal lines there are in order to do the question. I know once i rearrange the equation i can find the angle, by the way i rearranged it to be O = sin inverse [(n-1/2)(wavelength)/d}.
     
  2. jcsd
  3. Oct 2, 2009 #2

    Delphi51

    User Avatar
    Homework Helper

    Just go on n = 1, 2, 3, ... until your calculator blows up!
    (that is, until you get a sine value greater than 1).
    You must have missed drawing all those crest circles and interference lines in high school. You can actually see a pattern and get a formula for the number of lines. I think it is 4 times the number of wavelengths of separation, counting both destructive and constructive lines.
     
  4. Oct 3, 2009 #3
    Sorry, i'm still not following unfortunately..
     
  5. Oct 3, 2009 #4

    Delphi51

    User Avatar
    Homework Helper

    dsin A = (n-1/2)(wavelength)
    sin A = (n-1/2)(wavelength)/d
    A = inverse sin[(n-1/2)(wavelength)/d]
    When n = 1, A = invSin(1/2*1.2/2.5) = invSin(0.24) = 13.9 degrees
    When n = 2, ...
     
  6. Oct 3, 2009 #5
    ohh okay i thought thats what you meant. So i honestly just keep doing that until i get to a whole number?
     
  7. Oct 3, 2009 #6

    Delphi51

    User Avatar
    Homework Helper

    Yes, keep going. You'll know when to stop.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Wave Interference Question
Loading...