Why the image on a tv screen is distorted when an air plane passes low?
Distortion of picture on a television receiver
When an aircraft passes low overhead, the picture on the T V screen is distorted. In fact, the transmitting antennae of TV is transmitting waves in all directions. Some of them go directly to the receiving aerial and some of them reaches the aerial after reflected from the aircraft. Since the aircraft is in motion, the path difference of the direct and reflected from the airplane waves continuously changes. When it is satisfying the condition of constructive interference, the image on the screen becomes brighter and when it satisfies the condition of destructive interference, the screen is black or the image is dim.
Note that the reflected wave from the airplane is usually weak, i-e, its amplitude is smaller. Therefore, in case of destructive interference the crest and trough do not completely cancel one another and there is a resultant amplitude. Therefore, the image becomes dimmer and usually not completely dark.