2. 外语
  3. What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器). Almost everyone has

What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器). Almost everyone has

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问题     What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器).
    Almost everyone has noticed the frightening appearance of animals at night, as their eyes seem to glow in reflected light. One may think that just as reflective highway signs alert the motorists to many road hazards, so early man was often warned of danger by light from his campfire reflected in the eyes of lurking(潜伏)predators. In both cases, the light is ret-roreflected, giving it a particularly bright appearance.
    The principles of retroreflection have been understood for centuries. However, it is only within the last fifty or sixty years, with the wide use of the automobile, that this area of optics(光学)has received important commercial application. Today, the uses of retroreflective materials are many. They are applied to bicycles and motor vehicles to make them more visible at night. And they assist pilots by improving the visibility of runway markers.
    Large sums are spent for retroreflective materials, but purchasers have often found it difficult to specify performance for the materials they buy. Performance is of concern not only from the standpoint of the brightness of reflected light, but also from the standpoint of its color. It is important, for example, that the yellow hues(色调)in warning signals be of consistent color quality on all road signs so the driver can rely on color, as well as shape, to discern the signs’ meanings. Seven colors — silver, blue, yellow, red, green, brown and orange — are currently used for marking the interstate highway system.
Retroreflective materials have been used extensively since the invention of______ .
选项 A、the automobile
B、the laser beam
C、photography
D、highways
答案A
解析 本题属于事实细节题，提问的是反向发射器在什么发明以后才被广泛应用。依据是第三段前两句，人们了解反向反射原理虽然已有数百年，但直到汽车被广泛使用，它才具有了重要的商业用途。这说明，反向反射材料的广泛应用是从汽车被发明之后才开始的。所以答案为A)。
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