问题 计算题

(1)(4分)下列说法中正确的是        

A.X射线穿透物质的本领比γ射线更强

B.红光由空气进入水中,波长变长、颜色不变

C.狭义相对论认为物体的质量与其运动状态有关

D.观察者相对于频率一定的声源运动时,接受到声波的频率可能发生变化

(2)(4分)图示实线是简谐横波在t1=0时刻的波形图象,虚线是t2=0.2s时刻的波形图象,试回答:若波沿x 轴正方向传播,则它的最大周期为     s;若波的传播速度为55m/s,则波的传播方向是沿x轴     方向(填“正”或“负”)。

(3)(4分)一束光由空气射入某种介质中,当入射光线与界面间的夹角为30°时,折射光线与反射光线恰好垂直,这种介质的折射率为       ,已知光在真空中传播的速度为c=3×108m/s,这束光在此介质中传播的速度为      m/s。

答案

⑴CD;⑵0.8负; ⑶  

题目分析:(1)A、X射线穿透物质的本领比Y射线更弱.故A错误.红光由空气进入水中,频率不变,颜色不变,而波速变小,根据波速公式v=λf分析得知,波长与波速成正比,则波长变小.故B错误.根据狭义相对论得知,物体的质量与其运动状态有关,速度越大,物体的质量越大.故C正确.观察者相对于频率一定的声源运动时,如果两者距离变化时,接受到声波的频率可能发生变化.故D正确.

故选CD

(2)若波沿x轴正方向传播,传播时间,周期,当n=0时,T最大,最大值为.若波的传播速度为55m/s,波在△t=0.2s时间内传播的距离为,根据波形的平移法得到,波的传播方向是沿x轴负方向.

(3)当入射光线与界面间的夹角为30°时,入射角i=60°,折射光线与反射光线恰好垂直,则折射角r=90°-60°=30°,折射率为,这束光在此介质中传播的速度为

点评:本题是选修模块3-4部分的内容,常规题,考查的知识点比较全面.波动图象和折射定律是重点.

完形填空

第二节(共5小题;每小题2.5分,满分12.5分)

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

People know the dangers of fires. It’s good for a family to learn how to prepare for a fire. Here are some suggestions.

Put a smoke alarm in the house. The alarm makes a loud sound.   71    

Make escape plans. They should know all the ways out of the house. If there is a fire, everyone follows the plan to get out.   72  

Practise for a fire. They do fire practice because they teach children about fire safety.Everyone in the family should know the following fire rules:

Don't open a hot door! The fire can grow more quickly if you open the door. 73   Smoke can be more dangerous than fire. The best air is near the floor because smoke rises.

What will you do if your hair or clothes start to burn? First, don’t run! The fire burns faster because of more air. Drop! Fall to the floor. Then roll!    74    Put a blanket around you to keep air away from the fire that may still be on you.

There are many possible causes for fires.    75    If there is a fire, don’t forget to call 119 for help.

A.Turning over and over will make the fire go out.

B.Smoke from a fire causes the alarm to go off.

C.The cleanest air is found at the top.

D.Stay close to the floor!E. A wise family is ready all the time.

F. Make sure all the windows can be opened easily.

G. Do not go back to the house for any reason.

问答题