Many book, especially school book, have used pictures to help convey messages to simplify a meaning. The use of moving pictures or video can convey that meaning even more efficiently. As some words like "green" can not be completely described by words, action too can not be completely understood without motion. Though attempts at showing movement can be illustrated by use of arrows and such, fully understanding motion can best be described by the motion itself.
A bit of warning though. This does not only apply to factual and good teaching, it also applies to lies and evil ways. Adolf Hitler used the media including television to convey his messages and by doing so he grew in popularity quickly among the German people. He also controlled the media so that opposing views or harmful images where left out. Any tool used for good can also be used for evil but that does not mean that the tool is bad just that it works.
It is really only dependent on learning style. Some student enjoy watching a documentary and while others prefer to read a book and take notes. Book learning isn't necessarily "better' and TV learning isn't necessarily "worse." Some kids zone out when reading monotonous books and some zone out when watching repetitive documentaries.
I feel that books have their place and are the traditional way to learn about certain things. That being said, I can see where a television would be a useful medium for teaching. As for it being a better tool, though, I doubt that. I suppose it might be the case if the child is an auditory learner, but the main trouble that I see with televisions is that it is much easier to zone out, as they call it, than it is with books. Books require a bit more active process on the part of the person to interact with, whereas television is the definition of passive.
I don't mean to say you can't educate yourself on TV (watching a documentary on a historical event on HistoryChannel or watching debates or even a travel program or just by watching good films--not subjective, meaning, not good for you but good overall--) but today's TV is filled with reality TV protagonized by equally low people who don't demonstrate a high degree of intelligence. Kim Kardashian is supposed to be a really nice person in real life but in her show she's a total airhead.
Television is not a better teacher for teens than books. Television programming, the majority of the time, is created for entertainment purposes only. In addition, books activate the learning part of the brain while TV does not. TVs only make us receptive to information. Books require us to process information and think about it in more depth.
Although watching some television can be educational, it is imperative that teens learn to read well. Reading is used everyday and the comprehension needs to be there for all of us. Anyone can watch television, but not everyone can read. Without a good basis in reading, everything in life is difficult, including getting a degree.
I believe there are a lot educational programs available but I have my doubts teenagers would chose them if given options. Books can contain far more information and cover far more topics than educational TV and they are by far a better source for learning. While TV isn't useless I don't find it to be a better teacher for teens over books.
I do not think television is better for teaching teens things, however I do not think books are better either. Some people learn better from the word and from text while others learn better from hands on seeing the experience take place. It is hard to say what is better for everyone.