7. In a large water tank experiment, water waves are gener- ated with straight, parallel wave fronts, 3.00 m apart. The wave fronts pass through two openings 5.00 m apart in a long board. The end of the tank is 3.00 m beyond the board. Where would you stand, relative to the perpendicular bisector of the line between the openings, if you want to receive little or no wave action? 8. A page in a student's notebook lists the following informa- tion, obtained from a ripple tank experiment with two point sources operating in phase: n = 3, X3 = 35 cm, L = 77 cm, d = 6.0 cm, 03 = 25, and 5 crests = 4.2 cm. Calculate the wavelength of the waves using three methods. 9. Two very small, identical speakers, each radiating sound uniformly in all directions, are placed at points S and S as in Figure 8. The speakers are connected to an audio source in such a way that they radiate in phase, at the common wavelength of 2.00 m. Sound propagates in air at 338 m/s. (a) Calculate the frequency of the sound. (b) Point M, a nodal point, is 7.0 m from S, and more than 7.0 m from S2. Find three possible distances M could be from S. (c) Point N, also a nodal point, is 12.0 m from S and 5.0 m from S2. On which nodal line is N located? S T M 5.0 m 12.0 m S2 5.0 m N Figure 8