Let us be clear that the picture we see on the TV screen is not really there at all. Had we slowed down the whole process at a given point of time, there would be one speck on the screen. It is the speck of the fluorescent material being hit by the beam at that point of time. The whole picture is an aggregate of such thousands of specks appearing one by one over  a period of time. It is due to the speed of scanning the screen by the electron beam, we perceive the full picture. It is called persistence of vision. It is a normal feature of human eye-sight. In TV, our eyes are not able to detect the time intervals between the spots of light, and we find continuity in them.A common example is a burning incense stick which you can move rapidly in a circle. The different dots of light form a full circle of light as the human eye is not able to detect the distance between the different dots.