题干

氢原子的部分能级示意图如图所示,大量电子从n=4跃迁到n=2的能级时,发出可见光a,从n=3跃迁到n=2的能级时,发出可见光b,下列说法正确的是:

A:在同一种介质中可见光a的波长小于可见光b的波长

B:大量电子从n='4' 跃迁到n='3' 的能级时,发出紫外线

C:在同一种玻璃中a的传播速度大于b的传播速度

D:对于某种金属如果a光能发生光电效应,则b光也一定能发生光电效应

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答案(点此获取答案解析)

A

同类题5

    阅读下面四篇短文,从每题所给的A、B、C、D四个选项中选出最佳选项。

C

    When Matty Sallin,34,was working on a degree in art and technology at New York University,he got interesting homework in electronics class.He decided to create an alarm clock(闹钟).

    "Everybody has to deal with these every day,and they are really unpleasant!"he says.He asked different people what they would like to wake up to instead of a noisy alarm.A lot of them said,"The smell of bacon(培根肉)".

    So Sallin and two classmates invented a new kind of alarm clock:a wooden box with a pig face and a digital clock that uses the smell of cooking bacon instead of the sound to wake someone up.He explains."There's no danger of burning,because I built it carefully.It uses halogen light bulbs(卤素灯)instead of a fire for cooking and turns off automatically after ten minutes.Yes,the clock itself can do it.Just a few easy steps are needed to set the alarm."

    "What you do is to put some frozen bacon in the night before and set the alarm,"says Sallin.

    "If you set the alarm for 8:00,it will turn on at 7:50 and slow cook for ten minutes under the halogen bulbs."he says,Then the bulbs turn off and a fan blows the smell out through the nose of the pig.

    "So instead of an alarm,  ▲,"says Sallin."Then you can open the door on the side and pull the bacon out and eat it."

    When Sallin was a kid,he spent a lot of time making drawing of inventions."I wanted to make an lift in my backyard and a special tree house."he says."But I never really thought I'd be called an inventor!"

    Sallin got an A in the class and went on to other things—but people continue to hear about his invention and email him every day asking where they can buy his alarm clock.