将一个大烧杯倒扣在桌面上，里面充以烟雾，用手电筒通过烧杯底自上而下照射，调节手电筒的聚光圈，使通过烟雾的光组成粗细均匀的柱形光束，如图所示：
（1）烧杯内充以烟雾，其作用是______．
（2）烧杯底上放一个凸透镜，观察到的现象如图乙所示，说明凸透镜对光有______作用．
（3）烧杯底上放一个凹面镜，观察到的现象如图丙所示，说明凹透镜对光______作用．
（1）当光照到烟雾时，烟雾颗粒对光的反射方向是不同的，会发生漫反射现象，所以我们从各角度可以看到光的路径；
（2）当在烧杯底放一个凸透镜时，发现光路聚集，说明凸透镜对光线有会聚作用；
（3）如果放置凹透镜，发现光路是发散的，说明凹透镜对光线有发散作用；
故答案为：（1）烟尘微粒对光的漫反射来显示光通过的路径；（2）会聚；（3）发散．
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| We should show respect (尊重) to everybody, especially our elders because they are ahead of us-in age, in wisdom, in experience and education. Our 1 have done a lot for us, directly or indirectly and most of us 2 everything to their kindness and love. When we 3 them respect, whether ii is by bowing to them, or 4 them with a smile, or offering them any help they need, it is one way of 5 our own love and gratitude (感激) to them. 6 , elders have also been through all the years you are 7 and know a little more about the world than you do. It is 8 that you do not agree with the belief of your elders but this is nothing new. All younger generations have always 9 with their elders and it is these differences that bring changes in human 10 . However much you disagree with them, give them credit (信任) for their 11 . With changing times and 12 influences, youngsters no longer know what is interpreted as disrespect to elders. Youngsters should 13 express their views and if there are arguments, they should not 14 their voices. If there is no space on sofas or chairs, children will immediately 15 their places, and sit on the carpet. In buses and trains, youngsters are 16 to give up their places to older people. This is not a 17 of who has more rights. It is simply that those who are youngsters have the strength to bear 18 , or stand unpleasantness, so it is natural to show consideration (体贴) to those who are older and perhaps at a 19 disadvantage (劣势). When you do simple things as a mark of respect, elders become 20 that youngsters care for them, and they respond with affection and kindness. | ||||
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