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Two-slit interference

  • Thread starter fwFAWFSERG
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  • #1
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SOLVED

Homework Statement



A two-slit interference set-up with slit separation d =0.30 mm produces interference fringes at a particular set of angles THETAm (where m = 0, 1, 2,) for red light of frequency f = 4.9×10^14 hz.

If one wishes to construct an analogous two-slit interference set-up that produces interference fringes at the same set of angles THETAm for room-temperature sound of middle-C frequency f = 262 hz, what should the slit separation distance be for this analogous set-up?
this particular problems answer is 640 but i cant seem to arrive at that

Homework Equations


sin(theta)= m(wavelength)/d

The Attempt at a Solution


i believe sin(theta) is equalin both, so i dont see why it wouldnt come down to wavelenth/d is proprotional to wavelenth/d, or converting to frequency 1/fd = 1/fd or fd=fd.
 
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Answers and Replies

  • #2
674
2
You know [tex]\lambda = v/f[/tex], but they both have different velocities so you can't use fd = fd.
 
  • #3
11
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arent their velocities equal at c, being the speed of light?
 
  • #4
674
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room-temperature sound of middle-C frequency f = 262 hz
Sound doesn't travel at the speed of light. At least not where I live at.
 
  • #5
11
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oh that is quite true, shouldnt have overlooked that, so i can now say the formula is
c/fd = 343/fd?

edit: yes i can, thanks alot nickjer, i got it now.
 

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