Concave and Convex Lenses
by Riya T. 2011
What Are Concave and Convex Lens?

A convex lens makes objects look farther away. Convex lenses also correct farsightedness. Concave lenses makes objects look smaller and closer and correct nearsightedness. If you do not have a proper balance of concave and convex, the object will look like an illusion. Concave and Convex curvatures of lenses bends, or refracts, light in opposite ways, depending on the focal length of the lens and on the distance between the lens and the object, giving either a smaller or a larger image of an object. Light rays are reflected inwards toward a focal point by concave mirrors. A concave mirror can produce images that are right side up and very large or upside down. Light rays are reflected outwards by a convex mirror. Images produced by a convex mirror will always appear right side up and smaller than the actual object. Light rays are refracted as they pass through translucent objects such as lenses. A concave lens is thicker at the edges than it is at the center, and a convex lens is thicker in the middle than it is at its edges. A concave lens refracts light rays spreading them outward producing an image that is upright and smaller than the actual object. A convex lens refracts light rays inward. If a convex lens is held close to a person’s eyes, they will see an image that is upright and larger than the actual object. If the convex lens is held further away from a person’s eyes, they will see an image upside down. A refracting telescope uses two convex lenses to magnify images in the sky. A reflecting telescope uses a concave mirror, a plane mirror, and a convex lens to do the same job. A microscope, like a reflecting telescope, uses a concave mirror, a plane mirror, and a convex lens. However, they are used to magnify very small images on slides, not in the sky.

This picture is a visual representation on how light refracts of both concave and convex lenses.

What Does Concave and Convex Mean?

Concave means “hollowed or rounded”.
Convex means “curved or rounded like the outside of a sphere or circle”.

This is a picture showing the light bending off a concave and convex lens, starting or ending from the focal point.

What is the difference between concave and convex lenses?

The difference between a convex lens and a concave lens is that a convex lens bends light rays toward each other and a concave lens spreads light rays apart. Curved surfaces concave, which means they turn inward, or convex, which means that they curve outward. The mirrors we use see our reflection is flat because although the images they produce are reversed from right to left, they are the same size and shape as the object. Curved mirrors produce distorted images that can be larger or smaller than the object reflected. Convex lenses are thicker in the middle than at the edges. They refract toward the center. Only people have convex lenses. Concave lenses are used in telescopes and glasses. Concave lenses are thinner in the middle than at the edges. When light passes through, concave lenses always bend away from each other toward the edges of the lens.

Concave Lens and Mirrors

Concave lenses are lenses that are thinner at the center than at the edges, bend light rays so that they diverge, and so they produce only virtual images. Light reflected from concave mirrors are focused in front of them. Depending on how close the object is, either. A concave lens is a lens that possesses at least one surface that curves inwards. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A concave lens is thinner at its center than at its edges, and is used to correct short-sightedness (myopia). The image formed by a concave lens depends on the position of the object. Concave mirrors are usually used for looking in the mirror for shaving or on makeup. For example, when you look in a mirror to see how your hair looks, you want to bend your head so the mirror will focus on your hair.

Convex Lens and Mirrors

Light reflected from concave mirrors is focused depending on how close the object is. Rays of light reflected from convex mirrors diverge, which makes them appear to have come from a focal point behind the mirror. The virtual image behind the mirror is smaller than the object, so convex mirrors are used as rear view mirrors in cars to help drivers see as much of the road behind as possible.

This is a diagram that I made to represent how concave lenses help with far-sightedness and convex lenses help with near-sightedness.


"Lens." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition.

Encyclopædia Britannica, Inc., 2011. Web. 19 Sept. 2011. ;

Lenses. Prod. Cochran. Cochran, 1988. Discovery Education. Web. 22 September 2011. ;

Refracted Light: Lenses: Convex and Concave. Prod. Audio Visual Inc.. Aims Multimedia, 1996. Discovery Education. Web. 22 September 2011.