While the history of technology can be traced along many lines, one of the most intriguing (引人入胜的) development is that photo technology, the technology of light．From the prehistoric invention of fire to laser beams (激光束)and fiber optics(光纤) , light has continually occupied the minds of inventors．'Their inventions fall into two groups-, the use of light to aid vision and, more interestingly, the use of light for purposes of communication.
The use of light for communication is one of the major directions that technology has taken ever since the middle of the nineth century．From still (静态的) photography to movies to television ( with a development from black-and-white to color imagery in each) , photo technology has had a great effect upon mass communication and mass education．Unlike the printed word, visual images have more impact because they are more immediate; They copy reality in a way that the printed word cannot．Unlike letter shapes, they are not abstract; unlike words, they require no symbolic interpretation by the mind．Combined with the widespread and uniform．spreading of such images, phototechnology affects the thinking of vast audiences and shapes their view of reality.
As the number of commercially available television channels grows, the viewer's of choice increases, but so does the burden of that choice.
It can be learned about the technology of light from the first paragraph that______.