The problem states: Waves broadcast by a 1152 kHz radio sta- tion arrive at a home receiver by two paths. One is a direct path, and the second is from re°ection o® an airplane directly above the re- ceiver. The airplane is approximately 137 m above the receiver, and the direct distance from station to home is 18:7 km. What is the height (within 1% error) of the airplane if destructive interference occurrs? Assume no phase change on reflection. Answer in units of m. First of all I am kind of confused as to where the receiver is...on the house or the radio station. I was thinking it should be on the house, but 137 meters seems very low for an airplane to be flying above a house. What I know/tried: I know that since it's destructive interference, it is out of phase, so we use ∆L=(lamda/2). and we can find L1 and L2 with the values given, but I have no idea how to include frequency...maybe using v=lamda/f? I tried applying the small angle approximation (where sinө~tanө), but the trigonometry is really confusing and I wasn't having much success. Could someone help?