SOLVED 1. The problem statement, all variables and given/known data 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 2. Relevant equations sin(theta)= m(wavelength)/d 3. 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.