章节大纲

  • A woman inserting a contact lens into her eye.

    The tiny object on this woman’s finger is life-changing for her. It lets her see clearly without wearing glasses. You probably recognize the object as a contact lens . You may even wear contact lenses yourself.
    ::这个女人手指上的细小物体是她的生命改变。 它让她看得很清楚,没有戴眼镜。 你可能认出该物体是隐形眼镜。 你甚至可以自己戴隐形眼镜。

    What Is a Lens?
    ::什么是镜头?

    A lens is a transparent object with one or two curved surfaces. It is typically made of glass (or clear plastic in the case of a contact lens). A lens refracts, or bends, light and forms an image. An image is a copy of an objected formed by the (or reflection) of visible light . The more curved the surface of a lens is, the more it refracts the light that passes through it. There are two basic types of lenses: concave and convex . The two types of lenses have different shapes, so they bend light and form images in different ways.
    ::透镜是一个透明的物体,有一个或两个弯曲的表面。它通常由玻璃制成(或隐形透镜的清晰塑料)。 透镜折曲或弯曲、 光和形成图像。 图像是可见光的反射( 反射) 所形成的反射的复制件。 透镜的表面越弯曲, 透透的光就越重。 有两种基本类型的透镜: 相形和相形。 两种透镜有不同的形状, 从而以不同的方式弯曲光和形成图像 。

    Concave Lens
    ::集中镜头

    A concave lens is thicker at the edges than it is in the middle. You can see the shape of a concave lens in the Figure . From the diagram, it’s clear that the lens causes rays of light to diverge, or spread apart, as they pass through it. Note that the image formed by a concave lens is on the same side of the lens as the object. It is also smaller than the object and right-side up. However, it isn’t a real image. It is a virtual image. Your brain “tricks” you into seeing an image there. The light rays actually pass through the glass to the other side and spread out in all directions. 
    ::圆形透镜在边缘比中间更厚。 您可以在图中看到圆形透镜的形状。 从图表中可以明显看出, 圆形透镜导致光线分解, 或者在穿过时分散。 请注意, 圆形透镜所形成的图像与物体在镜头的同一侧。 它也小于对象和右侧。 但是, 它不是一个真实的图像。 它是一个虚拟图像。 您的大脑“ tricks” 将看到一个图像。 光线实际上穿过玻璃向另一侧, 并分散到各个方向 。

    Shape of a concave lens illustrating light rays diverging through it, forming a virtual image.

    Convex Lens
    ::投影镜头

    A convex lens is thicker in the middle than at the edges. You can see the shape of a convex lens in the Figure . A convex lens causes rays of light to converge, or meet, at a point called the focus (F). A convex lens forms either a real or virtual image. It depends on how close the object is to the lens relative to the focus. 
    ::曲线透镜在中间比边缘更厚。您可以看到图中曲线透镜的形状。曲线透镜导致光线在焦点(F)的点聚集或相遇。曲线透镜形成真实或虚拟图像。它取决于对象与焦点的镜头之间的距离。

    Three diagrams illustrating how a convex lens forms real and virtual images.

    Q: An example of a convex lens is a hand lens. Which of the three convex lens diagrams in the Figure shows how a hand lens makes an image?
    ::Q: 曲线透镜的一个例子是手透镜。图中的三个曲线透镜图中,哪一个显示了手透镜如何制作图像?

    A: You’ve probably looked through a hand lens before. If you have, then you know that the image it produces is right-side up. Therefore, the first diagram must show how a hand lens makes an image. It’s the only one that produces a right-side up image.
    ::A:你可能以前看过过手透镜。如果你有,那么你就会知道它产生的图像是右侧的。因此,第一个图表必须显示一个手透镜如何生成图像。 这是唯一能生成右侧图像的图。

    Summary
    ::摘要

    • A lens is a transparent object, typically made of glass, with one or two curved surfaces. A lens refracts light and forms an image.
      ::透镜是一个透明的物体,通常由玻璃制成,有一两个弯曲的表面。透镜折射光,形成图像。
    • A concave lens is thicker at the edges than it is in the middle. This causes rays of light to diverge. The light forms a virtual image that is right-side up and smaller than the object.
      ::圆形透镜在边缘的厚度比中间的厚。 这导致光线分裂。 光形成一个虚拟图像, 它向上和小于天体。
    • A convex lens is thicker in the middle than at the edges. This causes rays of light to converge. The light forms a real or virtual image depending on the distance of the object from the lens. 
      ::二次曲线透镜在中间的厚度比在边缘的厚。这导致光线汇合。光形成真实的或虚拟的图像,视对象与镜头的距离而定。

    Review
    ::回顾

    1. What is a lens? What does it do?
      ::镜头是什么?它能做什么?
    2. Describe the image formed by a concave lens.
      ::描述由混凝土镜头形成的图像 。
    3. Explain how a hand lens forms an enlarged image of an object.
      ::解释手透镜如何形成一个对象的放大图像。