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GRE Subject Test · GRE Physics หัวข้อ 8 4:04 การบรรยายภาษาอังกฤษ · คำบรรยายภาษาอังกฤษ + 中文 ลอยตัวบนภาพ
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Transcript
A semiconductor's conductivity depends on the states and carriers available, not just on how many electrons the material has.
半导体的电导率取决于可用的状态和载流子，而不只是材料中电子的数量。
This topic uses band and carrier pictures, applies radioactive decay and binding energy, and checks conservation laws in particle reactions.
本主题使用能带和载流子图像，应用放射性衰变和结合能，并检验粒子反应中的守恒定律。
Filled bands cannot carry ordinary current without accessible nearby states.
满带若无可接近的邻近能态，则无法传导普通电流。
Metals have partially filled or overlapping bands; semiconductors have a small band gap.
金属具有部分填充或重叠的能带。 半导体具有较小的能隙。
Donor and acceptor doping change carrier populations.
施主和受主掺杂会改变载流子浓度。
Fermi–Dirac occupancy is 1/ .
费米-狄拉克占据数等于1除以e的(E−μ)/(kT)次方加1。
At zero temperature it becomes a step at the Fermi energy; thermal broadening does not make every state half occupied.
在绝对零度时，它变为费米能级处的阶跃函数。 热展宽不会使所有态都半占据。
Radioactive populations obey N equals N sub zero e to the minus lambda t.
放射性原子核数目遵循 N = N₀e^(−λt)。
Activity is lambda times N, and half-life is natural log of 2 divided by lambda.
活度为 λN，半衰期为 ln2/λ。
Binding energy comes from a mass deficit multiplied by c squared. Compare binding energy per nucleon when discussing stability.
结合能来自质量亏损乘以 c²；讨论稳定性时，请比较每个核子的结合能。
Nuclear and particle processes must conserve charge, energy, momentum and the applicable quantum numbers.
核反应与粒子过程必须满足电荷、能量、动量以及相应量子数的守恒。
Beta decay includes a neutrino or antineutrino; a two-body electron-only story cannot explain its continuous energy spectrum.
β衰变中会包含中微子或反中微子。 仅考虑两体电子的模型无法解释其连续能谱。
Binding energy is the positive energy needed to pull a nucleus apart into free nucleons.
结合能是把原子核拆分为自由核子所需的正能量。
For a reaction, the energy released, Q, is the initial rest mass minus the final rest mass, times c squared.
对一个反应，释放的能量 Q 等于初态静止质量减去末态静止质量，再乘以 c²。
A mass decrease of 0.0040 atomic mass units releases 0.0040 times 931.5 mega-electron-volts: 3.73 MeV.
质量减少 0.0040 原子质量单位，释放的能量为 0.0040 乘 931.5 兆电子伏特，即 3.73 MeV。
Positive Q means energy release.
正的Q值表示能量释放。
Charge, nucleon number, energy and momentum must still balance; Q alone does not establish a reaction rate.
电荷、核子数、能量和动量仍须守恒；仅凭Q值无法确定反应速率。
A neutral stationary parent nucleus decays into two neutral fragments with masses m and 3m.
一个中性静止的母核衰变为两个中性碎片，质量分别为 m 和 3m。
Released kinetic energy is Q, small compared with either rest energy.
释放的动能为 Q，与任一碎片的静止能量相比很小。
Find each fragment's kinetic energy and speed ratio.
求每个碎片的动能及速度之比。
Four marks.
四分。
Momentum conservation gives equal and opposite momenta of magnitude p.
动量守恒给出大小均为 p、方向相反的动量。
Nonrelativistic energies are K sub 1 equals p squared over 2 m, and K sub 2 equals p squared over 6 m, hence ratio 3 to 1.
非相对论动能分别为 K_1 = p^2 / (2m) 和 K_2 = p^2 / (6m)，因此比值为 3:1。
Their sum is Q, so K sub 1 equals 3 Q over 4, and K sub 2 equals Q over 4.
两者之和为 Q，故 K_1 = 3Q/4，K_2 = Q/4。
Speeds obey v sub 1 divided by v sub 2 equals p divided by m, all over p divided by 3 m, which equals 3.
速度满足 v_1 / v_2 = (p/m) / (p/(3m)) = 3。
Award momentum, energy ratio, partition, and speed ratio.
请给出动量、能量比值、分配及速度比值。
Equal momentum does not mean equal energy.
相等的动量并不意味着相等的能量。
Activity and surviving population both decay, but their units differ: activity is transitions per second.
活度和剩余粒子数都会衰减，但它们的单位不同。 活度的单位是每秒衰变次数。
band gap: An energy interval with no allowed bulk electronic states in the band model.
带隙。 一个在能带模型中没有允许体电子态的能量区间。
half-life: Time for a radioactive population to halve.
半衰期。 放射性原子核数量减半所需的时间。
Retrieve the meanings without reading the definitions, then change a parameter in the original transfer and test the limiting case.
在不阅读定义的情况下回忆其含义，然后改变原始传递中的一个参数并检验极限情况。