内部反思共计

Total internal reflection allows the light to travel down the optical fiber and not pass through the sides of the tube.  The light continuously reflects from the inside of the tube and eventually comes out the end. Optical fibers make interesting lamps but they are also used to transport telephone and television signals.
::总的内部反射使光线能够从光纤下行,而不会穿过管的两侧。光线从管内不断反射,最终从底端出来。光纤造就了有趣的灯,但也用来传送电话和电视信号。

Total Internal Reflection
::内部反思共计

We already know that when light passes from one medium into a second medium where the index of refraction is smaller, the light refracts away from the normal.
::我们已经知道,当光从一个介质过往到第二个介质,折射指数较小时,光的折射就会脱离正常。

In the image below, the light rays are passing into an optically less dense medium; therefore, the rays bend away from the normal.  As the angle of incidence increases, the light ray bends even further away from the normal.  Eventually, the angle of incidence will become large enough that the angle of equals $\begin{align*}90^\circ\end{align*}$  , meaning the light ray will not enter the new medium at all.
::在下面的图像中,光线正传入光学密度较低的介质中; 因此, 光线会向正常方向弯曲。 随着事件角度的增加, 光线会向更远的正常方向弯曲。 最终, 光线的角会变得足够大, 以致于光线不会进入新的介质 。

Consider a ray of light passing from water into air.  The index of refraction for air is 1.00 and for water is 1.36.  Using Snell’s Law , $\begin{align*}n_i \sin \theta_i=n_r \sin \theta_r\end{align*}$ , and allowing the angle of refraction to be $\begin{align*}90^\circ\end{align*}$ , we can solve for the angle of incidence which would cause the light ray to stay in the old medium.
::考虑从水到空气的光线。空气的折射指数是1.00,水的折射指数是1.36。用Snell的法则, nisini=nrsinr,并允许折射角度为90,我们可以解决导致光线停留在旧介质中的发光角度。

$\begin{align*}n_i \sin \theta_i = n_r \sin \theta_r\end{align*}$
::尼西尼i=nrsinr

$\begin{align*}(1.36)(\sin \theta_i) = (1.00)(\sin 90^\circ)\end{align*}$
:1.36)(sini)=(1.00)(sin90)

$\begin{align*}\sin \theta_i = 0.735\end{align*}$ and $\begin{align*}\theta_i=47^\circ\end{align*}$
::i=0.735和i=47

This result tells us that when light is passing from water into air, if the angle of incidence exceeds $\begin{align*}47^\circ\end{align*}$ , the light ray will not enter the new medium. The light ray will be completely reflected back into the original medium.  This is called total internal reflection . The minimum angle of incidence for total internal reflection to occur is called the critical angle .
::这个结果告诉我们,当光从水中传入空气时,如果发光角度超过47°Q,光线将无法进入新介质。光线将完全反射回到原始介质中。这称为完全内部反射。总内部反射的最小发光角度被称为关键角度。

Total internal reflection is the principle behind fiber optics . A bundle of fibers made out of glass or plastic only a few micrometers in diameter is called a light pipe since light can be transmitted along it with almost no loss. Light passing down the fibers makes glancing collisions with the walls so that total internal reflection occurs.
::总内部反射是光纤背后的原则。 由玻璃或塑料制成的一连串纤维,直径只有几微米,被称为光管,因为光线可以随光线传来,几乎不会丢失。 光线传下来,纤维会与墙壁碰撞,从而产生整体内部反射。

Use the Diamond Cut simulation below to adjust the shape of a diamond with the three sliders related to depth, crown, and table size. Try to find a combination of sliders for which the light is trapped inside - achieving total internal reflection - and a very sparkly diamond! 
::使用下面的钻石剪切模拟来调整钻石的形状, 并使用与深度、 冠状和表体大小有关的三条滑块来调整。 试着找到各种滑块的组合, 这些滑块的光被困在里面 — 实现完全的内部反射 — 以及一颗非常闪亮的钻石 !

Summary
::摘要

播放段落
• When light passes from one medium into a second medium with a smaller index of refraction, the light refracts away from the normal.
  ::当光从一个介质进入第二个介质,且折射指数较小时,光的折射线会远离正常。
播放段落
• If the angle of incidence becomes large enough that the angle of refraction equals $\begin{align*}90^\circ\end{align*}$ , the light ray will not enter the new medium with the smaller angle of refraction.
  ::如果事件角度变得足够大, 折射角等于 90 , 光线就不会以小折射角进入新介质 。
播放段落
• Total internal reflection means the light ray will not enter the new medium but will be completely reflected back into the original medium.
  ::整体内部反射意味着光线不会进入新介质,而是将完全反射回原介质。

Review
::回顾

播放段落
1. Find the critical angle for light passing from diamond into air, given  $\begin{align*}n_{\text{diamond}} = 2.42\end{align*}$ .
   ::找到从钻石向空气中传递光的临界角,给 ndiamond=2.42。
播放段落
2. When two swimmers are under water in a swimming pool, it is possible for the interface between the water and the air to act as a mirror, allowing the swimmers to see images of each other if they look up at the underside of the surface.  Explain this phenomenon.
   ::当两个游泳者在游泳池水下时,水与空气之间的界面可以作为镜子,让游泳者在看地表下方时能够看到彼此的图像。请解释这种现象。
播放段落
3. Robert shines a laser beam through a slab of plastic and onto the interface between the slab of plastic and the air on the other side.  The index of refraction for the plastic is 1.62.  If the angle of incidence in the plastic is $\begin{align*}54^\circ\end{align*}$ , will the laser beam pass out of the plastic into the air?
   ::罗伯特通过塑料板板和塑料板与另一侧空气的界面照射激光光束。塑料折射指数为1.62。如果塑料的发照角度是54,激光光束是否会从塑料板中传入空气中?

Explore More
::探索更多

Use this resource to answer the questions that follow.
::使用此资源回答下面的问题 。

播放段落
1. What phenomenon occurs when the light does not enter the new medium and remains in the old medium?
   ::当光线不进入新介质并留在旧介质中时,会发生什么现象?
播放段落
2. When does this phenomenon occur?
   ::这种现象何时发生?