【OG24-618题】The passage implies that if tunneling time reached no maximum in increasing with barrier thickness, then_mofa留学圈mofaGRE在线题库系统_GRE在线搜题_GRE题库解析_GRE真题机经_GRE课程_GRE培训机构

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Most attempts by physicists to send particles faster than the speed of light involve a remarkable phenomenon called quantum tunneling, in which particles travel through solid barriers that appear to be impenetrable. If you throw a ball at a wall, you expect it to bounce back, not to pass straight through it. Yet subatomic particles perform the equivalent feat. Quantum theory says that there is a distinct, albeit small, probability that such a particle will tunnel its way through a barrier; the probability declines exponentially as the thickness of the barrier increases. Though the extreme rapidity of quantum tunneling was noted as early as 1932, not until 1955 was it hypothesized—by Wigner and Eisenbud—that tunneling particles sometimes travel faster than light. Their grounds were calculations that suggested that the time it takes a particle to tunnel through a barrier increases with the thickness of the barrier until tunneling time reaches a maximum; beyond that maximum, tunneling time stays the same regardless of barrier thickness. This would imply that once maximum tunneling time is reached, tunneling speed will increase without limit as barrier thickness increases. Several recent experiments have supported this hypothesis that tunneling particles sometimes reach superluminal speed. According to measurements performed by Raymond Chiao and colleagues, for example, photons can pass through an optical filter at 1.7 times the speed of light.

The passage implies that if tunneling time reached no maximum in increasing with barrier thickness, then

tunneling speed would increase with barrier thickness tunneling speed would decline with barrier thickness tunneling speed would vary with barrier thickness tunneling speed would not be expected to increase without limit successful tunneling would occur even less frequently than it does

正确答案： D

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文章大意逻辑
文章开篇指出物理学家让粒子超光速运动常涉及量子隧穿现象，即粒子能穿过看似不可穿透的固体屏障。接着介绍量子理论中粒子隧穿的概率情况。然后提到1932年就注意到量子隧穿的极快速，1955年Wigner和Eisenbud提出隧穿粒子有时超光速的假设，依据是粒子隧穿时间随屏障厚度变化的计算，超过一定厚度后隧穿时间不再增加，意味着隧穿速度会无限制增加。最后说明近期一些实验支持了该假设。 文章类型及逻辑简图
文章类型：现象理论假设验证逻辑简图： Phenomenon: Physicists use quantum tunneling to try to send particles faster than light, particles travel through impenetrable like barriers. Theory: Quantum theory about particle tunneling probability. Hypothesis: In 1955, Wigner and Eisenbud hypothesized tunneling particles sometimes travel faster than light based on calculations of tunneling time and barrier thickness. Verification: Recent experiments support the hypothesis. 问题类型及做题方法
问题类型：推断题。做题方法：根据题干中“tunneling time reached no maximum in increasing with barrier thickness”定位到文中关于隧穿时间和屏障厚度关系以及由此对隧穿速度影响的描述部分进行推断。 选项分析
A选项：“tunneling speed would increase with barrier thickness”。文章中不是简单说速度随厚度增加，而是在达到最大隧穿时间后速度无限制增加，该选项不准确，排除。 B选项：“tunneling speed would decline with barrier thickness”。与文章理论和假设不符，文章说的是可能超光速及相关变化，不是速度下降，排除。 C选项：“tunneling speed would vary with barrier thickness”。表述太笼统，没有准确反映出在特定条件下（最大隧穿时间）速度的变化情况，排除。 D选项：“tunneling speed would not be expected to increase without limit”。根据原文，当隧穿时间不会随屏障厚度增加而达到最大值时，就不会出现超过最大隧穿时间后速度无限制增加的情况，该项符合推断，当选。 E选项：“successful tunneling would occur even less frequently than it does”。题干讨论的是隧穿时间和速度的关系，此选项说的是隧穿成功的频率，话题不一致，排除。

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