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  • 光的折射

    Lesson Objectives
    ::经验教训目标

    • Demonstrate that light travels in a straight line until it strikes an object or travels from one medium to another.
      ::证明光线以直线运行,直到击中物体或从一个介质到另一个介质。
    • Demonstrate that light can be reflected, refracted, and absorbed.
      ::证明光线可以被反射、分解和吸收。

    Lesson Vocabulary
    ::词汇表课程

    • light - a form of energy that travels in waves and can move through empty space where there is no air
      ::光光光 - 一种能量形式,在波浪中穿行,可以在没有空气的空空空空间中移动
    • transmit - pass through
      ::- 通过
    • reflection - bouncing back of light from a surface
      ::- 反射反射从表面光线反弹背面
    • refraction - bending of light
      ::折射 - 灯光弯曲
    • absorb - light is taken in
      ::- 吸收 - 光被吸收

    Is this a magic trick? Is this straw really broken? The answer to both questions is no. There’s nothing wrong with the straw. No magic is involved, only science. This is an example of how light behaves. What you are seeing is how light reacts when it enters a new substance. 
    ::这是魔术吗?这个稻草真的坏了吗?对这两个问题的答案是否定的。稻草没有错。没有魔法,只有科学。这是光的表现的一个例子。你看到的是光在进入新物质时的反应。

    Speed of Light and Matter (Advanced Topic)
    ::光速和物速(高级专题)

    You have probably heard of the famous equation E = mc 2 . The "E" represent the amount of energy. The "m" represents mass. The "c" represent the speed of light. Writing a "c" is much easier than writing the actual speed of light. The speed of light is a really large number. 
    ::您可能听说过著名的等式 E = mc2. “ E” 代表能量量。 “ m” 代表质量。 “ c” 代表光速。 写入“ c” 比写光速要容易得多。 光速是一个非常大的数字 。

    The speed of light is about 300 million meters per second. That's really, really fast. Light always travels at the same speed through space. In outer space, there is not any matter to get in its way. Think about riding your bicycle. When you ride on a hard surface, it is easy to pedal. You can go really fast. Imagine how your speed would change if you were riding through deep sand. You would find it hard to pedal. You would not be able to go as fast. The same is true for light. When there is no matter around, like in outer space, it can go fast. When matter gets in its way, it slows down. 
    ::光速是每秒约3亿米。 这是真的, 真的非常快。 光总是以同样的速度穿梭于太空中。 在外层空间, 没有什么问题可以阻碍它。 想想骑自行车。 当你骑在硬的表面时, 踏板很容易。 你可以走得非常快。 想象一下如果骑在深沙中, 你的速度会如何变化。 你会发现踏板很难。 你无法以同样的速度飞过太空。 光是同样的情况。 当周围没有问题的时候, 就像在外层空间一样, 它可以飞得很快。 当事情进入其轨道时, 它会放慢速度。

    Light travels through some matter faster than through others.  Table   gives the speed of light in six common materials.
    ::光通过某种物质的速度要快于其他物质,表格显示六种共同材料的光速。

    Material Speed of Light (m/s)
    Air 299 million meters per second
    Water 231 million meters per second
    Glass 200 million meters per second
    Vegetable oil 150 million meters per second
    Alcohol 140 million meters per second
    Diamond 125 million meters per second

    No matter how slow light travels, it still goes really, really fast. The important thing to remember is that it does travel. It is hard for us to imagine light taking time to cover a distance.
    ::不论光速如何缓慢,它仍然非常非常、非常快。重要的是记住它确实能够行走。我们很难想象光能花时间来覆盖距离。

    Think about when you enter your science classroom. You step through the door. You tell your teacher, "Hello." You walk to your desk and sit down. It may take around 10 to 20 seconds to walk this distance. Imagine now your teacher turns the light off. She carries a small lamp over to the door you just entered.  She asks you to watch carefully as she switches on the light. She flips the switch and you immediately see the light. The light just covered the same distance you just walked. That's how fast light is. For us, it is hard to imagine that it moves. 
    ::仔细想一想,当你进入你的科学教室时, 你走进门, 告诉老师, “你好。” 你走到你的书桌坐下, 可能要花10到20秒的时间走这条距离。 想象一下, 现在你的老师把灯关了, 她把一小盏灯带到你刚进来的门上。 她要求你在她开灯时仔细看一看。 她打开开关, 你立即看到灯。 灯光覆盖的距离与你刚刚走过的距离相同。 光线是如此之快。 对我们来说, 很难想象它会移动。

    Now let's think about light traveling between the Sun and Earth. The Sun is 93 million miles away. What if we were able to turn off the Sun for just a second? How long would it take us to notice? Would we notice instantly like in the classroom? Remember, the Sun is a long way away. 
    ::现在让我们考虑一下太阳和地球之间的光线旅行。太阳距离9300万英里。如果我们能把太阳关掉一秒钟呢?要多久我们才能注意到?我们会像教室里一样立即注意到太阳吗?记住,太阳离地球很远。

    We wouldn't notice the change for a little over 8 minutes. That is because the Sun is a long way away. Even when moving as fast as light, it takes time to travel from the Sun to Earth. What do you think happens when it hits the air in our atmosphere? Air is made up of matter. When light travels through matter it slows down. How do scientists know it slows down? What evidence do scientists have? 
    ::我们不会在8分钟内注意到变化。 这是因为太阳离太阳很远。 即使在光速如此之快的移动中, 从太阳到地球需要时间。 当太阳击中大气层的空气时, 你认为会发生什么? 空气是由物质构成的。 当光通过物质时, 它会放慢速度。 科学家们怎么知道它会减慢速度? 科学家们有什么证据呢 ?

    When sunlight hits Earth's atmosphere it bends just a little. If sunlight goes through water droplets it bends even more. The bending of light through droplets of water is why we can see rainbows. It also explains why the straw in a glass of water appears to be broken. 
    ::当阳光照射地球大气层时,它会弯曲一点。如果阳光穿过水滴,它会弯曲更多。光通过水滴弯曲,这就是为什么我们能够看到彩虹的原因。它也解释了为什么玻璃水中的稻草似乎被打破。

    Bending Light
    ::发光灯

    When light passes from one medium (or type of matter) to another, it changes speed. You can actually see this happen. If light strikes a new substance at an angle, the light appears to bend. This is what explains the straw looking broken in the picture above. 
    ::当光从一个介质(或物质类型)移到另一个介质(或物质类型)时,光会改变速度。你实际上可以看到这种情况发生。如果光照到一个角度,光线似乎会弯曲。这就是上面图片中看破的稻草的原因。

    So, does light always bend as it travels into a new medium? If light travels straight into a new substance it is not bent. You may know this angle as perpendicular. The light still slows down, just does not appear to bend. Any angle other than perpendicular the light will bend as it slows down. The bending of light is called  refraction .  Figure   shows how refraction occurs. Notice that the angle of light changes again as it passes from the glass back to the air. In this case, the speed increases, and the ray of light resumes its initial direction. 
    ::因此,光向向新介质移动时,是否总是弯曲?如果光直通新物质,它不会弯曲。你可能知道这个角度是垂直的。光仍然会放慢,只是看起来不会弯曲。光向的弯曲会随着其减速而弯曲。光的弯曲被称为折曲。图显示如何发生折射。注意光的角在从玻璃向空气穿透时会再次变化。在这种情况下,光的速度会加快,光的光线会恢复其最初的方向。

    For a more detailed explanation of refraction, watch this video: 
    ::更详细地解释中伤情况,

     

     

    Diagram of refraction

     

    Lesson Summary
    ::经验教训摘要

    • Light always travels at the same speed through empty space. The speed of light is about 300 million meters per second. When light travels through matter, it travels more slowly.
      ::光以同样的速度穿梭于空隙中。光速约为每秒3亿米。当光穿透物质时,光行慢。
    • If light passes from one type of matter to another at an angle, the light changes speed and bends. This bending of light is called refraction.
      ::如果光从一种物质到另一种物质的角度,光会改变速度和弯曲。光的弯曲被称为折射。
    • The amount at which light refracts depends on the type of matter it enters.
      ::光分形的大小取决于其进入的物质类型。

    Lesson Review Questions
    ::经验回顾问题

    1. What is the refraction of light? When and why does it occur?
      ::什么是光线的折射?它何时和为什么发生?
    1. Draw a diagram to show how visible light refracts when it passes from air to diamond.
      ::绘制图表以显示从空气到钻石的可见光分形。