题干

如图所示为氢原子的能级示意图,一群氢原子处于n=3的激发态,在向较低能级跃迁的过程中向外发出光子,用这些光照射逸出功为2.49eV的金属钠,下列说法正确的是()

A:这群氢原子能发出三种频率不同的光,其中从n=3跃迁到n=2所发出的光波长最短

B:这群氢原子能发出两种频率不同的光,其中从n=3跃迁到n=1所发出的光频率最高

C:金属钠表面所发出的光电子的初动能最大值为11.11eV

D:金属钠表面所发出的光电子的初动能最大值为9.60eV

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D

同类题4

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    My folks bought their first house in the early 1940s after Dad got a better job in Marquette, Michigan. We lived just inside the city limits in what was still a rural area.

    In the spring of 1948, when I was 6 years old, my parents bought a calf (小牛) to replace our cow, which had been killed the year before. So one day we drove to a local farm and returned with a white and brown calf we named Tubby.

    We didn't own a truck, so Tubby rode home in the backseat of Dad's car with my 9-year-old brother Steve, and me. As you can imagine, the trip was a lot of fun for us kids.

    Later that summer, Mom thought it would be cute to take a picture of me sitting on Tubby's back. All went well unti1 the snap of the camera shutter sent Tubby charging off on a run, with me holding on for dear life. I lasted for about 30 feet before I hit the ground. Mom was quick enough to shoot a follow-up picture, so we had photos of me both on and off Tubby!

    When summer had passed, the day arrived for poor Tubby to fill our freezer I must have been somewhere else with my Mom on the fateful day, because I have no memory of how it happened. All I knew was that the barn was empty, and that we had plenty of meat for dinners.

    I hadn't lived on a farm like my mother, so I didn't understand that what happened to Tubby was not unusual. Livestock aren't meant to be pets, and most farm kids know and accept that truth.

    Whenever we had beef for dinner, I would tearfully, “Is this Tubby” This went on for a couple of weeks until Dad had finally had enough and declared, “No more cows!” That made me feel a little better about poor Tubby.