#ScienceWithGray — Television Multipath Effects, The Reasons For Distortions During TV Display

- By Aan Gray ✒️
It's well observed that all waves are subject to reflection and refraction: these two phenomena are responsible for some of the mods common problems with television receptions.

You may have noticed that the image on your television screen is sometimes afflicted by 'ghosting', where a second image appears horizontally displaced from the true image. This is caused by tee reflection of the television signal from hills, buildings and even aircraft! The reflected signal will arrive a little later than the direct signal, and the television set will display this signal a little later in its scan across the screen. So the ghost image appears. This effect is usually avoided using a properly oriented, directional antenna pointing towards the nearest television transmitter. In this case, only the direct signal is detected, unless the reflected signal happens to arrive from exactly the same direction as the direct signal.
Refraction is responsible for a form of television interference known as 'multipath fading'. The refractive index of the earth's atmosphere is not constant, but varies with height and time. So waves can travel to the receiver along many different paths, both direct and refracted in the upper atmosphere. At the receiver, the interference of the multipath signals can cause the image to fade for a while. Reception problems caused by refraction are enhanced by particular atmospheric conditions, which is why weather forecasters can sometimes predict when television reception will be poor.
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