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【单选题】

The History of the Atomic Bomb On August 2, 1939, just before the beginning of World War II, Albert Einstein wrote to then President Franklin D. Roosevelt. Einstein and several other scientists told Roosevelt of efforts in Nazi Germany to purify uranium-235, which could be used to build an atomic bomb. It was shortly thereafter that the United States Government began the serious undertaking known then only as 'The Manhattan Project'. Simply put, the Manhattan Project was committed to expediting research that would produce a viable atomic bomb. The most complicated issue to be addressed in of an atomic bomb was the production of ample amounts of 'enriched' uranium to sustain a chain reaction. At the time, uranium-235 was very hard to extract. In fact, the ratio of conversion from uranium ore to uranium metal is 500:1. Compounding this, the one part of uranium that is finally refined from the ore is over 99% uranium-238, which is practically useless for an atomic bomb. To make the task even more difficult, the useful U-235 and nearly uselessU-238 are isotopes(同位素), nearly identical in their chemical makeup. No ordinary chemical extraction method could separate them only mechanical methods could work. A massive enrichment laboratory/plant was constructed at Oak Ridge, Tennessee. Harold C. Urey and his colleagues at Columbia University devised an extraction system that worked on the principle of gaseous diffusion, and Ernest O. Lawrence (inventor of the Cyclotron) at the University of California in Berkeley implemented a process involving magnetic separation of the two isotopes. Next, a gas centrifuge was used to further separate the lighter U-235 from the heavier, non-fissionable U-238. Once all of these procedures had been completed, all that needed to be done was to put to the test the entire concept behind atomic fission ('splitting the atom', in layman's terms). Over the course of six years, from 1939 to 1945, more than $2 billion was spent during the history of the Manhattan Project. The formulas for refining uranium and putting together a working atomic bomb were created and seen to their logical ends by some of the greatest minds of our time. Chief among the people who unleashed the power of the atom was J. Robert Oppenheimer, who oversaw the project from conception to completion. Finally, the day came when all at Los Alamos would find out if 'The Gadget' (code-named as such during its development) was going to be the colossal dud of the century or perhaps an end to the war. It all came down to a fateful morning in midsummer, 1945. Which of the following is the least possible reason for the launching of the Manhattan Project?

A.
Franklin D. Roosevelt.
B.
Nazi Germany.
C.
Albert Einstein and other scientists.
D.
The Second World War.
题目标签:同位素
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举一反三

【单选题】下列属于同位素的一组是

A.
H2O和D2O
B.
金刚石和石墨
C.
氕、氘、氚
D.
40K、40Ca

【单选题】For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of where the Earth’s only satellite came from. But now there is direct eviden...

A.
the differences between the Earth and the Moon
B.
how man manages to set foot onto the Moon
C.
the collision between the Earth and the Moon
D.
the origin of the Moon

【单选题】同位素中()。

A.
质子数相同,中子数不同
B.
质子数相同,中子数相同
C.
中子数相同,质子数不同
D.
中子数、质子数均不相同

【单选题】同位素()

A.
质子数与中子数均相同,且原子核处于相同能量状态的一类原子
B.
具有相同质子数的一类原子
C.
质子数相同但中子数不同的核素
D.
质子数与中子数均相同,但原子核处于不相同的能量状态的核素
E.
原子核处于不稳定状态,需要通过核内调整或能级调整才能趋于稳定的核素
相关题目:
【单选题】下列属于同位素的一组是
A.
H2O和D2O
B.
金刚石和石墨
C.
氕、氘、氚
D.
40K、40Ca
【单选题】For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of where the Earth’s only satellite came from. But now there is direct eviden...
A.
the differences between the Earth and the Moon
B.
how man manages to set foot onto the Moon
C.
the collision between the Earth and the Moon
D.
the origin of the Moon
【单选题】同位素中()。
A.
质子数相同,中子数不同
B.
质子数相同,中子数相同
C.
中子数相同,质子数不同
D.
中子数、质子数均不相同
【单选题】同位素()
A.
质子数与中子数均相同,且原子核处于相同能量状态的一类原子
B.
具有相同质子数的一类原子
C.
质子数相同但中子数不同的核素
D.
质子数与中子数均相同,但原子核处于不相同的能量状态的核素
E.
原子核处于不稳定状态,需要通过核内调整或能级调整才能趋于稳定的核素