2. 职称英语
  3. The nature of light is not wholly known, but it is generally believed to be

The nature of light is not wholly known, but it is generally believed to be

游客2023-11-10  25
问题     The nature of light is not wholly known, but it is generally believed to be matter, as in its(1)______, it obeys the laws(2)______matter. So closely is it connected with heat and electricity that there can be (3)______ doubt of their all being(4)______ different modifications of the same substance. The effects of light(5)______ other bodies and how light is affected by them(6)______ some important principles.
    Rays of light are reflected from one surface to(7)______. It is by this reflection of light that objects are(8)______ visible. However, unless light falls directly(9) ______the eye they are invisible, and are not(10)______felt until after a certain series of operations upon the various coverings of the eye. Smooth and(11)______surfaces reflect light most powerfully, and send to the eye the images of the objects (12)______ the light proceeded before reflection. Glass would be of no use to us as a mirror, were it not first(13)______on one side, interrupting the rays in their(14)______from the glass into the air. The reason why trees, rocks and animals are not all mirrors is that their surfaces are(15)______, and rays of light reflected from such a surface are(16)______in every direction. Stand before a mirror and your image is formed and appears to be as far(17)______the glass as you are before it. Rays of light(18) ______reflected at the same(19) ______at which they fall upon a mirror, two persons can stand in (20)______ position that each can see the image of the other without seeing his own. [br] (9)
选项 A、upon
B、in
C、off
D、down
答案 A
解析 介词辨析题。fall upon表示“落到……上”，符合文意，故[A]upon为正确答案。fall in表示“到期；集合，排队”；fall off表示“下降，脱落”；fall down表示“失败，倒塌”。
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