2 URGENT questions on Wave Phase Differences [Diagram Included]! Two microwave sources S( and S, are situated as shown in Fig. 5.1. The waves emitted by the two sources are in phase and are polarised in the same plane. http://img190.imageshack.us/img190/3924/wave1f.jpg [Broken] A microwave detector is placed on a line XY which is parallel to, and 3.2 m from, the line joining S, and S2. M is the midpoint of the line joining S( and S2. The line from M perpendicular to the line S,S2 meets XY at O. The detector produces an output which is proportional to the displacement of the wave. With only S, switched on, the change with time of the detector output measured at P, a distance of 5.0 cm from O, is as shown in Fig. The waveform detected at P for S2 only is also shown on Fig. Determine phase difference between the waves at P. My solution: According to my knowledge, phase difference= Δt/T x 2π Hence, looking at the distance between the two peaks or two troughs, the time lag is about 0.2 (x10s) Dividing by period of 8.3 (x10s) you get around π/2. Is this correct? Is there a better method to do this? Second part (Still same question): S1 and S2 are switched on together, with the emitted waves in phase. The detector is moved from P along the line OY, in the direction away from O. State and explain the approximate distance that the detector must be moved before the intensity is a maximum, given that there is no maximum between O and P. My solution: Since constructive interference occurs, path difference=nλ. Since it is first maximum, n=1. But I do not know how to carry on. Anyone please help? Another Question: http://img687.imageshack.us/img687/446/wave2.jpg [Broken] Fig shows a displacement-distance graph for two sound waves A and B. of the same frequency and amplitude. WaveA travelling to the right and wave B is travelling to the left. (ii) The period of each wave is T. Determine the maximum displacement of the resultant of the two waves 1. at the instant shown. 2. at the instant shown +1/8T, 3. at the instant shown +3/8T. Well guys, Im really unsure on how to do this question, with all the 1/8T and 3/8T which are confusing me. Anyone help? Thanks.