问题 选择题

如图所示,一条光线由空气射到半圆形玻璃砖表面的圆心O处,在玻璃砖的半圆形表面镀有银反射面.则下图中几个光路图,能正确、完整表示光线行进过程的是(  ).

答案

答案:D

光射到玻璃砖的上表面发生反射和折射,折射光经下表面反射再回到上表面,又发生反射和折射. 同理反射光到达下表面再反射至上表面也发生反射和折射.根据光路可逆原理可知D项正确.

阅读理解

__小题1:___  Scientists and experts have proved the uniqueness of finger-prints and discovered that no exactly similar pattern is passed on from parents to children, though nobody knows why this is the case.

The ridge (隆起) structure on a person's fingers does not change with growth and is not affected by surface injuries. Burns, cuts and other damage to the outer part of the skin will be replaced in time by new one, which bears a reproduction of the original pattern.小题2:   Some criminals make use of this fact to remove their own finger-prints but this is a dangerous and rare step to take.

Finger-prints can be made very easily with printer's ink. They can be recorded easily.

___小题3:___ Because of the simplicity and economy of this system, finger-prints have often been used as a method of solving criminal case. A suspected man may deny a charge but this may be in vain. ___小题4:___ .

When a suspect leaves finger-prints behind at the scene of a crime, they are difficult to detect with the naked eye.  ___小题5:___ . Some of the marks found are incomplete but identification is possible if a print of a quarter of an inch square can be obtained.

A.Special techniques are used to "develop" them.

B.A fingerprint is an impression of the friction ridges of all part of the finger.

C.It is only when the inner skin is injured that the arrangement will be destroyed.

D.With special methods, identification can be achieved successfully within a short time. E. A latent(隐约的)print is the chance reproduction of the friction ridges deposited on the surface of an item.

F. His finger-prints can prove who he is even if his appearance has been changed by age or accident.

G. Every human being has a unique arrangement of the skin on his fingers and this arrangement is unchangeable.

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