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So, you might ask then well what is the significance of shooting different amounts of photons at a metal?
所以，你们可能会问向,金属发射不同数量的光子,有什么重要性？
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So we can actually pop an electron or eject an electron from any single orbital that is occupied within the atom.
任何一个被占据轨道,打出一个电子,或者说发射出一个电子。
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Being and void, being and void, so now I've got my plus two little projectile coming in, and plus two zooms right through.
有和无，有和无，现在带两个正电荷的发射体进来了，两个正电荷正好穿过。
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Studies using imaging techniques like CAT scans, PET, and fMRI, illustrate that different parts of the brain are active during different parts of mental life.
应用电脑断层扫描,正电子发射断层扫描,以及功能性核磁共振成像,等成像技术的研究,表明不同的心理活动,会导致不同大脑区域的激活
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Imagine you got this monster cannon to fire things.
设想你有一门火力强劲的大炮发射炮弹
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So what we're saying here is the incident energy, so the energy coming in, is just equal to the minimum energy that's required to eject an electron.
这里我们来讨论一下，入射能量正好等于,发射出一个电子所需要的最低能量的情况。
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So that means we're going to need to figure out what is the energy per photon that's emitted by that UV light.
所以那意味着我们将需要,计算出从紫外光源发射出的,每个光子的能量。
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So, the take-home message is whether you have three photons or 3,000,000 photons that you're shooting at your metal, if you're not at that minimum frequency or that minimum energy that you need, nothing is going to happen.
所以，这里表明的信息是,无论是向金属发射3个光子,还是300万个光子,如果没有达到所需的最低频率,或者最小能量,什么事情都不会发生。
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Typically, these are recent imaging methods like CAT scan and PET scan and fMRI which, as I said before, show parts of your brain at work.
通常是应用现代的成像技术来进行研究,比如电脑断层扫描,正电子发射断层扫描技术,以及功能性核磁共振成像,正如我之前所说,这些技术可以让你看到大脑的活动区域
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The electron's going to come out of that highest occupied atomic orbital, that one that's the highest in energy, because that's going to be the at least amount of energy it needs to eject something.
这个电子应该是从,最高的被占据轨道上出来的，它的能级是最高的，因为这样的话发射出它,只需要消耗最少的能量。
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It makes sense that it's going to come out of the highest occupied atomic orbital, because that's going to be the lowest amount of energy that's required to actually eject an electron.
从最高占据轨道上,去掉一个电子是合理的，因为这样是发射一个电子,所损失的最低能量。
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And when we talked about that, what we found was that we could actually validate our predicted binding energies by looking at the emission spectra of the hydrogen atom, which is what we did as the demo, or we could think about the absorption spectra as well.
当我们讨论它时，我们发现,我们可以通过,观察氢原子,发射光谱，来预测，结合能，就像我们在演示实验里做的那样，或者我们也可以观察吸收谱。
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What about the energy of the emitted photons?
发射光子的能量怎么样？
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Absorption is just the opposite of emission, so instead of starting at a high energy level and dropping down, when we absorb light we start low and we absorb energy to bring ourselves up to an n final that's higher.
吸收就是发射的逆过程,与从一个高能量到低能量不同，当吸收光时，我们从低能量开始,吸收能量到一个更高的能量。
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And what we have left over is this amount of energy here, which is going to be the kinetic energy of the ejected electron.
都用来发射它,剩下的这些就是,出射电子的动能。
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Photon emission, perhaps.
光子发射，可能。
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We're only using up a little bit to eject the electron, then we'll have a lot left over.
如果我们只需要用很少一部分来发射出电子，那么我们可以得到很多的剩余能量。
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So we can use an equation to relate the incident energy and the kinetic energy to the ionization energy, or the energy that's required to eject an electron.
因此我们可以用一个公式将入射能量,与动能和电离能，就是发射出一个电子所需要的能量关联起来。
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So this means that we can go directly from the energy between two levels to the frequency of the photon that's emitted when you go between those levels.
这意味着我们可以直接,从两个能级的能量得到它们之间,跃迁发射出光子的频率。
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So I said before when we were talking about single atoms, we always define the zero energy as when an electron was actually ejected, but now, when we talk about chemical reactions taking place, it's very, very rare that we're actually going to be talking about anything that gets to this point here.
我之前说过，当我们讨论单个原子的时候，我们总是把零点能,定在电子被发射出去以后，但是现在，当我们讨论化学反应发生的时候，非常非常罕见出现，确实达到,这种程度的情况。
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we start high and go low, we're dealing with emission where we have excess energy that the electron's giving off, and that energy is going to be equal the energy of the photon that is released and, of course, through our equations we know how to get from energy to frequency or to wavelength of the photon.
当我们从高到低时，我们说的,是发射,电子有多余的能量给出，这个能量等于，发出,光子的能量，当然我们可以通过方程,从能量知道，光子的频率，和波长。
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if you don't want to use that, you can also derive it as we did every time, it should intuitively make sense how we got there. But the exams are pretty short, so we don't want you doing that every time, so we'll save the 2 minutes and give you the equations directly, but it's still important to know how to use them.
吸收的和发射的，如果你不想用公式,你也可以每次都向我们这样推导它,很直观的就能得到结果，但考试时间很短，我们不希望你们每次都推导,所以我们会直告诉你，让你节省2分钟，但知道如何应用它十分重要。
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So, for example, when people, and we'll talk about this next class, were looking at different characteristics spectra of different atoms, what they were seeing is that it appeared to be these very discreet lines that were allowed or not allowed for the different atoms to emit, but they had no way to explain this using classical physics.
举个例子，当大家看到,不同原子的特征光谱时,他们看到的是一些分离的线,那可以使不同的原子,发射或不发射出去，但是这些无法用经典物理来解释。
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So, for example, it's not just the 2 p that we could actually take an electron from, we could also think about ejecting an electron from the 2 s orbital.
比如，我们不只可以从，2，p，轨道上,打出一个电子，还能考虑从，2，s，轨道上,发射出一个电子。
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There is no way that you could irradiate a crystal of nickel with a single beam of x-rays and get that circular ring pattern if the electron beam were behaving as a particle beam only.
没有什么其他的途径,可以让镍晶体发射,单束X光来,继而得到环状图案,如果电子束,是以粒子束形式出现的。
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So let's do a sample calculation now using this Rydberg formula, and we'll switch back to emission, and the reason that we'll do that is because it would be nice to actually approve what we just saw here and calculate the frequency of one of our lines in the wavelength of one of the lines we saw.
让我们用Rydberg公式,做一个例题，我们回到发射上,这么做是因为这样,可以用我们看到的波长,来验证我们计算的频率。
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