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第三部分写作第一节One possible version:Best Spend Our Leisure TimeMost students think little of leisure time.In fact,onlyby taking full advantage of leisure time can we feel more re-laxed,happier and more energetic when returning to study.Here are some suggestions.If you are an active per-son,you can go on a picnic,or do sports,which can re-fresh you and make you happier when you face the fresh airand the fascinating scenery.For those who are not so ac-tive,you can listen to light music or read novels.In thisway,we can do much better with a light heart.

贮预神内还剁的约预体积为V剩一40V0一△V三22V。（1分)16.(1)ACD甲、乙两列波相遇时，振幅的最大值为Am=A,十A2=11cm,选项A正确；由图像和题意可知λ甲=4m2=2mT2=0.5s,同种介质中，机械波传播速度的大小相等，则有9=化，结合年一号吃一是解得m=心一4m/、T甲1s,选项B错误，C正确：由图像可知，(=0时刻甲、乙两列液的波谷沿轴方向的距离为d一10.5m一4m=6.5m,设to时刻两列波的波谷第一次相遇，在t时间内甲、乙两列波运动的距离之和为d一6.5m,则有d=(vm十vz)to,解得t=0.8125s,选项D正确；甲的振动传到x一10.5m处，需要的时间4-105一5s=1.375s,=1.25s时间内，甲的振动还未传到c-10.5m处，x410.5m处质点的路程2-立×4A2,结合A2一4cm,计算可得2=40cm,选项E错误(2)解：①由几何关系∠FEC=∠DEA=∠A=45°(1分)光线正好在AC边发生全反射临界角C-180°一∠FEC一∠DEA=45°(1分)2由折射率的定义可得n一品(1分)解得n=√2(1分)②光线DE射到AC边发生全反射后，反射光线EF与AB边平行由几何关系∠BFE=∠C+∠FEC=60°、∠EFP=2(90°-∠BFE)=60°、∠FPE=18O°-∠EFP-∠FEC=75°(1分)过B做EF的垂线与EF的交点为G,BG-DE-AD-L,EG-DB-L (1)BG-tanG∠BFE,EF=EG+GF(1分)解得EF-Q+号)L1分在△EFP中由正弦定理可得mPEn界EPEFFP(1分)联立可得FP-2L,DB+EF+FP=e+D(1分)