填空题

The word laser stands for "light amplification by stimulated emission of radiation". To many people lasers are very (36) ___________, but a laser is simply a (37) ___________that produces a very strong light. The light from a laser is called (38) ___________ light because it is light that moves in only one direction. In contrast, incoherent light, like the light form the sun or a light , (39) ___________, moves away from its (40)___________in all directions and (41) ___________in a narrow beam. As soon as the laser was developed, scientists began thinking of practical (42)___________for it. One of the earliest uses was to make extremely (43)___________measurements of distance and speed. As time passed, many more applications for the laser were developed. (44)______________________________. From laser printers to technology by which whole encyclopedias of information can be stored on a laser disk (called a CD-ROM) and read by a computer, lasers are revolutionizing computers. Lasers have also made a big difference in the way telephones work. Instead of changing sound waves to electricity that travels through copper wire, (45) _________________________________. One such fiber can carry more than a million conversations at the same time! (46)_____________________________________.