What is a concave and convex lens?

Katherine W.


Concave lens definition:

The concav
concave lens oppisite of magnifing glass KW.jpg
Figure 1
e lens is also called the diverging lens because it diverges the light rays. The Concave lens curves inward and the middle is the thinnest making the object looks smaller then it is supposed to be. Concave lens corrects near sightedness. Opposite: Convex lens

Figure 1

Convex lens definition:

Is the opposite of concave lens and is also called the converging lens. The lens curves outward and the middle is thicker making things look larger than it actually is. Convex lens does that by gathering the light to focus on the object. Convex lens corrects far sightedness.

convex lens magnifiyn glass KW.jpg
Figure 2

Figure 2

Examples of lenses:

Concave: There are many different examples of concave lenses. Many things have both concave and convex lenses together like an eyeglass, some mirrors, and a carmera. The concave lens helps the convex lens have a sharper image.

Convex: Convex lenses are very popular because there are many tools that will help humans see things far away. This includes the telescope, microscope, or binoculars. The telescope was invented by Hans Lippershey and microscope was invented by Zacharias Janssen.

History of lenses:

Lenses were used for many things all over history. The oldest artifact of a lens is a Nimrud lens estimated over three thousand years old. One of the earliest records of lenses was from Ancient Greece where they talked about using the lens to reflect light and make fire. The lens was first wildly used in Europe when the invention of the spectacle was invented.

How the lenses work:

When the light goes through the lens, depending on if it is a convex or concave lens, the outcome of the size when you look into the lens will be different. The concave lens will show the object smaller because the light rays go out and change direction of the path when it goes through the lens. This causes the light rays to not have a focus point and make the object look smaller than it really is. The convex lens is the opposite, it makes things look bigger. The lens does that by focusing the light rays on the object and makes the object look bigger than it really is.

concave and convex lenses diagram.jpg
Diagram of the concave lens

Figure 3 (diagram of concave lens)
convex lens diagram KW.jpg
Diagram of the convex lens

Figure 4 (diagram of convex lens)


Diverge: Going with a different path then the others, separate.

Light: Something that is bright that helps you see in the dark/dim places.

Lens: A pieces of transparent material like glass that can be used to see.

Nimrud lens: Is a 3000 year old piece of rock crystal it is still a mystery what it is used for some suggest a magnifying glass while others think of it as a burning-lens (start fires because of the reflecting light.)

Near sightedness: Also called Myopia. Makes you see things clearly on places near you and blurry when the thing is far. (Opposite of far sidedness)

Far sightedness: Also called Hyperopia. Makes you see things clearly when they are far away from you and makes the things near you blurry. (Opposite of near sidedness)


"Lens." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition.Encyclopædia Britannica, Inc., 2012. Web. 13 Sept. 2012.

Site: Lewis, peter introducing physics light and sound. Tucson: brown bear books limited, 2010. Print

Site: Macaulay, David the way things work. New York City: New York, Houghton Mifflin Company, 1988, print

biconcave lens: standard forms of lenses. Art. Encyclopedia Britannica. Web. 24 Sept. 2012.

Wikipedia contributors. "Lens (optics)." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 23 Sep. 2012. Web. 24 Sep. 2012.

"Lens." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition.Encyclopædia Britannica, Inc., 2012. Web. 27 Sept. 2012.

"Lens (optics)." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 26 Sep. 2012. Web. 27 Sep. 2012.

"Nimrud lens." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 14 Sep. 2012. Web. 28 Sep. 2012.