题目

某同学采用如图所示的实验装置来研究光电效应现象．当用某一频率的光照射光电管的阴极 时，会发生光电效应现象，电流计中有电流通过．闭合电键 ，在阳极 和阴极 之间加上反向电压，通过调节滑动变阻器的滑片逐渐增大电压，直至电流计中电流恰好为零，此时电压表的电压值称为反向截止电压．现用频率为 的绿光照射阴极，测量到反向截止电压为 ，设电子电量为 ，普朗克常量为 ，则（） A . 逸出的光电子的最大初动能为 B . 阴极 的One Saturday afternoon, my daughter Alice asked me, “Are all people the same even if they are different in color?”I thought for a minute, and then I said, “I’ll explain, 1 you can just wait until we make a quick 2 at the grocery store（杂货店）. I have something 3 to show you. ”At the grocery store, we4 some apples --- red, green and yellow ones. Back home, I told Alice, “It’s time to 5 your question.” I put one apple of each 6on the table. Then I looked at Alice, who had a 7 look on her face. “People are like apples. They come in all 8colors, shapes and sizes. On the 9, some of the apples may not 10 look as the others. ” As I was talking, Alice was 11 each one carefully. Then, I took each of the apples and peeled（削皮）them, 12 them back on the table, but 13“Okay, Alice, tell me which is which.”She said, “I 14 tell. They all look the same now. ” “Take a bite of 15. See if that helps you 16 which one is which. ”She took 17, and then a huge smile came across her face. “People are 18 like apples! They are all different, but once you 19 the outside, they’re pretty much the same on the inside. ”She totally 20 it. I didn’t need to say or do anything else.1.A.althoughB.soC.becauseD.if2.A.stopB.startC.turnD.stay3.A.expressiveB.encouragingC.informativeD.interesting4.A.boughtB.countedC.sawD.collected5.A.checkB.mentionC.answerD.improve6.A.sizeB.typeC.shapeD.class7.A.worriedB.satisfiedC.proudD.curious8.A.ordinaryB.normalC.differentD.regular9.A.outsideB.wholeC.tableD.inside10.A.stillB.evenC.onlyD.ever11.A.examiningB.measuringC.drawingD.packing12.A.keepingB.placingC.pullingD.giving13.A.onB.towardC.forD.in14.A.mustn’tB.can’tC.shouldn’tD.needn’t15.A.each oneB.each otherC.the otherD.one another16.A.admitB.considerC.decideD.believe17.A.big bitesB.deep breathsC.a firm holdD.close look18.A.justB.alwaysC.merelyD.seldom19.A.put awayB.get downC.hand outD.take off20.A.madeB.tookC.gotD.did