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 Waves and Sound Waves and Sound Physics Help Forum Jan 16th 2015, 03:21 AM #1 Junior Member   Join Date: Oct 2014 Posts: 8 Help with basic question? Two points on a string at x=0 and x=1 are observed as travelling harmonic wave passes. The transverse displacements of the two points are: y1= 0.2sin(3PIt) and y2= 0.2 sin(3PIt+PI/8) I have to deduce the wavelength and speed of the waves, and decide if the conclusions are unambiguous. However, I've only met questions where I deduce these values from using 'k', and I see no way of attaining 'k' in these formulae, so I'm stumped. Any ideas? Thank you!   Jan 16th 2015, 06:27 AM #2 Physics Team   Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,352 Not sure what you mean by 'k,' but I suggest you become familiar with the general for a wave function: y(t) = A sin(wt+p) where A = amplitude, w (omega) = angular velocity in radians/second and p (often written as the Greek letter phi) is the phase shift of the wave. In this case point 2 is phase shifted by and angle of pi/8 from point 1, so therefore it is 1/16 of cycle away from point 1. Hence one answer is that the wavelength is 16 times the distance between the two points; but it may also be 1/16 + k cycles, where k = 1, 2, 3, .... since sin(wt + pi/8) = sin(wti + k + 2 pi) = sin(wt+pi/8 + 4 pi) = .... The speed of the wave comes from v = fL, where f = frequency in Hertz and L = wavelength. You can calculate frequency from f = w/(2 pi). Last edited by ChipB; Jan 16th 2015 at 11:49 AM.  Tags basic, question Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post bigdaddyJ Advanced Mechanics 1 Mar 20th 2015 12:09 PM Ry Snow Thermodynamics and Fluid Mechanics 4 Feb 5th 2011 06:39 AM lolly Kinematics and Dynamics 1 Jan 5th 2011 09:46 AM Akshay Quantum Physics 1 Sep 11th 2009 09:22 AM Raj Light and Optics 0 Oct 26th 2008 10:56 AM