propagation
US /ˌprɑpəˈɡeʃən/
・UK /ˌprɒpə'ɡeɪʃn/
B2 中高級多益
n. (u.)不可數名詞宣傳
The propagation of health information is helpful
n. (u.)不可數名詞繁殖；增殖
The propagation of these plants is difficult
影片字幕
我把頭髮染成了長春花藍色，嘗試了捲髮女孩的方法，給自己弄了個波波頭，結果哭了起來 (I dyed my hair periwinkle blue, tried the curly girl method, gave myself a bob and ended up crying)
24:58
- A jar like this is ideal for cuttings and propagation.
這樣的瓶子非常適合扦插和繁殖。
(Snapping a Steel Rod 1000x slower - The Slow Mo Guys)
05:12
- And even in slow-mo, it was instant. Absolutely instant. We'd probably need like, a million frames to get the propagation of that crack.
甚至在慢動作撥放時，它是瞬間。絕對是瞬間。我們可能會需要每秒一萬幀的相機才能拍到它被拉碎的瞬間
走進無線波的傳播 (Inside Wireless: Wave Propagation)
02:05
- Let's talk about some basic concepts in electromagnetic wave propagation.
讓我們來談談電磁波傳播的一些基本概念。
- So these were some basics of wave propagation.
以上就是有關波傳播的一些基本知識。
3.8 菲涅爾方程 (3.8 Fresnel Equations)
23:07
- We have a reflected electric field also lying in the plane of incidence e sub R We have a transmitted electric field We're going to call e sub T and the relationship between the incident field and the reflected field is given by those sets of equations The relationship between the incident field and the transmitted field is given by those sets of equations again The fields point in pretty much the same direction The electric fields in both cases are parallel to the plane of incidence Except the magnitude of the field the amount that gets through varies depending on the reflection coefficient And the transmission coefficient again very very similar the equations are slightly different but you do the calculation once you know the the Index of refraction on either side of the material the incident angle and from Snell's law you calculate the transmitted angle And again, let's stress is shown in the bottom that this is a wave coming in It's not just a line although we can represent it as a line and that the wave essentially maps an electric field to every point in space Given by planes that are perpendicular to the propagation direction of the wave So what you'll see in a lot of books or figures that look like this for s polarization We have the electric field sticking up out of the screen right at you for perpendicular Or excuse me for parallel or p polarization.
我們有一個反射電場，也位於入射面上 e sub R 我們有一個透射電場，我們稱之為 e sub T 入射電場和反射電場之間的關係由這兩組方程給出 入射電場和透射電場之間的關係也由這兩組方程給出這兩種情況下的電場都平行於入射面 除了場的大小外，透過的量取決於反射係數和透射係數 同樣非常相似，公式略有不同，但只要知道材料兩側的折射率和入射角，就可以進行計算，並根據斯涅耳定律計算出透射角、讓我們強調下圖中顯示的，這是一個波，雖然我們可以將其表示為一條線，但它並不只是一條線，而且從本質上講，波將電場映射到空間中的
- We need to talk about One of these cases is something called total internal reflection It turns out that if you have a wave coming from a material that has a high index of refraction So in this case in sub I is greater than in sub T As long as your angles of incidence are small or the the direction of propagation is Is pretty much close to the normal then things come out as you would expect you get a reflected field and transmitted field But as theta I increases and gets bigger as you're going from the material with higher index to the material with lower index essentially the direction case of T of This vector is going to move that way as the incident angle increases and at some point it's going to lie along the surface This means that all the radiation that comes in this direction is going to get reflected You're going to get a hundred percent reflection of the radiation and there's going to be no propagating radiation that goes out and this is called total internal reflection for the obvious reason that the total amount of the radiation gets Reflected from the surface going from a material of higher index into lower index The place this is most commonly used as an optical fibers because this is what keeps the light inside fibers to go very very long distances and Essentially if you want to calculate what the angle is the incident angle is where total internal reflection Starts to occur you simply use Snell's law you basically set theta T is equal to 90 degrees or greater and Essentially you can find that critical angle Let's call it theta C there is given the by the equation the sine of the critical angle is the Insub T the transmitted divided by the incident indices of refraction the second case we've also mentioned very briefly, but that's called Brewster's angle, and that's essentially the point where the Reflection coefficient of the parallel or P polarized electric field component is equal to zero right here in this case You get no reflection whatsoever And so for theta I equal to Brewster angles and Brewster angles given by that equation right there where theta B is Brewster angle so for theta sub I equal Theta sub B.
只要入射角度較小，或者傳播方向基本接近法線，那麼就會產生你所期望的反射場和透射場。但是，隨著θ I 的增大，從高折射率的材料到低折射率的材料，這個矢量的方向會隨著入射角的增大而移動，並在某一點上沿著表面移動。這就是所謂的全內反射，原因很明顯，輻射總量會從表面反射出去，從高折射率的材料進入低折射率的材料。你只需使用斯涅爾定律，基本上設定θ T等於或大於90度，就可以找到臨界角，我們稱之為θ C，它的公式是臨界角的正弦為Insub T，即傳輸的光線除以入射的折射率、在這種情況下，平行或 P 極化電場分量的反射
菲涅爾衍射解釋 (Fresnel Diffraction Explained)
09:27
- So in this video, we're gonna talk about Fresnel diffraction, or Fresnel propagation.
在本視頻中，我們將討論菲涅爾衍射或菲涅爾傳播。
- We can't use Fraunhofer diffraction for propagation through optical systems.
我們無法利用弗勞恩霍夫衍射法在光學系統中進行傳播。
線性偏振光和瓊斯微積分 (Linearly Polarized Light and Jones Calculus)
09:32
- This only depends on the material that we're propagating through, so if we know what the e-field is, we automatically know what the h-field is, and similarly we know its direction because it has to be orthogonal to the electric field, and e cross h is pointing in the direction of propagation, so it's our pointing vector.
這隻取決於我們所傳播的材料，所以如果我們知道什麼是 e 場，我們就會自動知道什麼是 h 場，同樣，我們也知道它的方向，因為它必須與電場正交，而 e 交叉 h 指向傳播方向，所以它就是我們的指向矢量。
- So let's say we know the direction of propagation of the plane wave, and let's say it's along the z-axis.
假設我們知道平面波的傳播方向，並假設它是沿著 Z 軸傳播的。
圓偏振光解析 (Circularly Polarized Light Explained)
10:50
- So let's say that this is the propagation direction of our plane wave and then we've got our coordinate axis.
假設這是平面波的傳播方向，然後我們就有了座標軸。
- And if we freeze the helix in time, we can see that it's a right-handed helix, so it follows the curve of our right-handed fingers as we point our thumb in the direction of propagation.
如果我們把螺旋線定格在時間上，就會發現它是一個右手螺旋線，所以當我們把拇指指向傳播方向時，它就會沿著我們右手手指的曲線移動。