College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 60

Figure P24.69 shows a radio-wave transmitter and a receiver, both h = 50.0 m above the ground and d = 600 m apart. The receiver can receive signals directly from the transmitter and indirectly from signals that bounce offthe ground. If the ground is level between the transmitter and receiver and a l/2 phase shift occurs upon reflection, determine the longest wavelengths that interfere (a) constructively and (b) destructively.