问题 单项选择题

在一根很长的弦线上(视为x轴),有两列波传播,其方程式为
y1=6.0×10-2cosπ(x-40t)/2(SI)
y2=6.0×10-2cosπ(x+40t)/2(SI)
它们叠加后形成驻波,则波节的位置是()。

A.x=2km

B.x=(2k+1)/2m

C.x=(2k+1)m

D.x=(2k+1)/4m

答案

参考答案:C

解析:

△[*]=πx=(2k+1)π(干涉减弱条件)

所以 x=(2k+1)m

阅读理解

My husband can plan wonderful surprise celebrations for me.Recently,however,I told him I didn’t want him to plan one for my upcoming birthday.

“Why?” he asked.

“I am embarrassed being the center of attention,”  I quickly explained.

Later,I began to think more deeply about this reason. Then I remembered the surprise celebration I had planned for my friend Nancy on her 60th birthday. We  were roommates on a three­week tour following the Silk Road on those famous steppes  (大草原)—and through the  mountains—of central Asia.

That  afternoon  we  had  arrived  at  our  hotel  in Samarkand,Uzbekistan. The young man at the hotel desk told me about a bakery about 10 minutes away. After giving me detailed directions,he added,“Your nose will let you know when you arrive there.”

The temperature was 40 ℃.Soon,my_olfaction proved to be an unfailing guide. Outside the bakery,a delicious smell greeted me.

There were several kinds of breads,cookies,and cakes on display. There were also beautiful iced cakes. I chose a cake topped with powdered sugar.

Later at the Karim Bek Restaurant,Nancy didn’t see the young waiter walk up the steps with the cake.When I began singing“Happy Birthday,”everyone at our table—except Nancy—joined in.

It took her a moment to realize what was happening. Then the grinning (咧嘴笑的)  guest of honor thanked me,blew out the candles on the cake,and ate three pieces of it.

Today,after reliving this experience in my mind,I told my husband to ignore my request.I now understand what a surprise party is about:It is not about having a surprise party but rather the delight in giving it. That is what brings the satisfying joy.

小题1:Why did the author go to the bakery?

A.To get some bread for her journey.

B.To experience the local taste in Samarkand.

C.To buy a birthday cake for her friend.

D.To eat some iced cakes to cool herself down.小题2:The underlined words “my olfaction” in Paragraph 7 most probably refer to________.

A.the waiter at the hotel

B.the author’s sense of smell

C.the author’s friend

D.the author’s map小题3:The party held at the Karim Bek Restaurant was________.

A.very successful

B.a little simple

C.quite boring

D.too noisy小题4:From the last paragraph we learn that now the author________.

A.becomes less interested in surprise parties

B.thinks surprise parties are embarrassing

C.enjoys giving others surprises

D.realizes the true meaning of surprise parties小题5:From the passage,we can NOT infer that________.

A.the author’s birthday is coming

B.the author’s husband loves her very much

C.the author and Nancy have been roommates for three weeks

D.the author has already spent her 60th birthday

单项选择题

Letter A

Dear Rose,

I like your programmes very much. I’m now writing to ask you something about American social customs. My American friends want me to join them in their dinner party. I am very happy and have decided to go, but I’m a little worried about it, too. The social customs in my country are very different from here, so I’m afraid of making mistakes.

Should I bring a present, such as sweets or flowers Should I arrive on time or a little late At the dinner table, how can I know which fork or knife to use How can I let the family know that I’m thankful for their kindness

Wang Lin

Letter B

Dear Wang Lin,

It’s a good idea to bring a small present when you go to a dinner party. Flowers are always nice, or you may bring a bottle of wine if you know that your friends drink it.

You should arrive on time or five to ten minutes late. Don’t get there early. If you’re going to be more than fifteen minutes late, you should call and tell them.

Try. to be free at the dinner table. If you don’t know about choosing the right fork or knife, just watch the other people, and follow them. If you still have no idea of what to do, ask the person next to you.

If you like the food, say so. Of course, you’ll thank them for the meal and for their kindness. It’s also a good idea to send a thank you card the day after.

Rose

If you’re asked to a dinner party but not sure about what to bring as a present, it’s good to bring()

A.some fruits

B.a bottle of wine

C.sonic flowers

D.a knife and fork