http://www.ck12.org Chapter 5. Energy
FIGURE 5.131
Convex Lens
A convex lens is thicker in the middle than at the edges. You can see the shape of a convex lens in theFigure5.132.
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. You can interact with an
animated convex lens at this URL: http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1395.msg5241#msg5241
Q:An example of a convex lens is a hand lens. Which of the three convex lens diagrams in theFigure5.132 shows
how a hand lens makes an image?
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.
Summary
- A lens is a transparent object, typically made of glass, with one or two curved surfaces. A lens refracts light
and forms an image. - 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. - 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.
Vocabulary
- lens: Transparent object with one or two curved surfaces that forms images by refracting light.
Explore More
At the following URL, vary the location of the object in the animation and observe what happens to the image. What
can you infer from your observations? http://www.physicsclassroom.com/shwave/lenses.cfm
Review
- What is a lens? What does it do?
- Describe the image formed by a concave lens.