[填空题]
Television and radio.qm d9y4 pnmgy7;u j1gvhv1 li3.h8i o waves reflecting from mountains or airplanes can interfere with the direct signal from .hvlvoihi1 8 3the station.
(a) What kind of interference will occur when 75-MHz television signals arrive at a receiver directly from a distant station, and are reflected from a nearby airplane 118 m directly above the receiver? Assume $\frac{1}{2}\;\lambda$ change in phase of the signal upon reflection.
(b) What kind of interference will occur if the plane is 22 m closer to the receiver?
