Radio waves (419m) from a station travel along two paths from the transmitter to a house. The first path is direct, 27km, and the second path is by reflection from a mountain directly behind the house. No phase change occurs upon reflection from the mountain. What minimum distance from the mountain to the house cases destructive interference?
The waves must be out of phase by half a wavelength for destructive interference, so the path difference Δ =2•s is equal to (n + ½)λ, or s = λ/4=419/4 =104.75 m.
