2019—2022英语周报外研45答案

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

34.(15分)【答案】(1)ABC(5分)(2)(1)y2613√2d()12c解析】1)如果波向x轴正方向传播t2-t=2+n,解得:T0.9(n=0,1,2,3…),波长为8m,波速v2n+1A=(40n+20)m/s(n=0,1,2,3……),同理可分析波向x轴负方向传播,情况相同,当n=2时,T=0.08s,故选项A正确;当n=2时,v=100m/s,故选项B正确;如果波源的振幼周期变为原来的2倍,机械波的传播速度由介质决定,则波长一定变为原来的2倍,故选项C正确;因为无论n取多少,T都不可能等于0.2s,所以质点振动的路程不可能是32m,故选项D错误;无论波沿x轴正方向传播还是沿x轴负方向传播,x=4m处的质点在t1和t2时刻的振动方向都是相反的,故选项E错误。(2)(10分)(1)光路如图所示,根据题意可知i=45°,根据几何关系可知:tan=A'B(1分)A'C1分)d且BC=BC(1分)BCAC=AB.-BC=3(1分B所以tan(1分)则sin分)折射率snz√26sIn r4(1分(n)光在玻璃板中的传播速度v=5(1分)传播距离s=(1分)cOS传播时间132d12(1分

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