Though invisible in normal light once it has hardened, this adhesive glows yellow when illuminated by a beam of ultraviolet of the sort often used in discotheques.
虽然粘着剂在普通光照下看不见，但一旦变硬便可以在紫外线光束的照射下变成黄色。
2
That means the beam produced is of higher quality than other lasers, is extremely straight (even by the exacting standards of a normal laser beam) and can thus be focused onto a small area.
(甚至符合正常激光束的严格标准)这样就能将能量集中传送到一个小的区域范围内。
3
The normal sonar system rotates its beam, either continuously or under the operator's control, and the position of maximum response to a particular echo is taken as the bearing of the target.