Difference between Convex and Concave Lens

Key Difference: Concave and convex are two basic types of lenses. A convex lens focuses light rays, whereas a concave lens causes the light rays to diverge.

A lens can be defined as a transparent material (like a glass) that has either an open curved surface or one flat surface or two curved surfaces. They work on the principles of refraction, as they change the direction of light waves by refraction. A convex lens focuses light rays, and therefore is also known as a converging lens. The focal point is the point where the light rays meet.

These types of lenses are thicker in the middle than in comparison to their edges. Due to this structure, it is able to converge the light rays. They produce real images, and therefore are mainly used in various optical instruments. A convex lens enables a thing to look bigger than its actual size. It happens due the fact that rays focus on the object and the object looks bigger than its actual size. Light that passes through a convex lens can be focused on a surface like a screen.

A concave lens is just the opposite of a convex lens. It is thinner in the middle and thicker at the edges. Therefore, it diverges the light rays. The emerging rays do not actually intersect. However, they seem to intersect on the incidence side by tracing the emerging rays backward.

This phenomenon is responsible for the creation of virtual images. Therefore, the image created by a concave lens is always a virtual image rather than a real image. They are unable to form an image on a screen. However, they are widely used together with convex lens in order to provide sharp images to the convex lens.

Comparison between Convex and Concave Lenses:





A concave lens is thinner in the middle and thicker at the edges.

A convex lens is thicker in the middle and thinner at the edges.

Other name

Diverging Lens

Converging Lens

Images Formed

Virtual, upright and smaller than the object between object and the lens. (regardless of the object's position)

Real , inverted, smaller than object, - object at F

Real , inverted, same size as object, - object at 2F

Real , inverted, larger than  object, object between 2F and F

No image -  object at F

Virtual, upright, larger than object – behind object on the same side of the lens


Concave means “hollowed or rounded”.

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

In Spectacles

Used for the correction of problem in short sight.

Used for the correction of problem in long sight.


Glasses (to correct for short sight), spy holes in doors, some telescopes, back window of coaches, etc.

Eye, camera, overhead projector, focus sunlight, projector microscope, simple telescope, glasses (to correct for long sight), magnifying glass, etc.

Focal Length



Image Courtesy: gcsescience.com, passmyexams.co.uk

Most Searched Non-Alcoholic Drinks Most Searched in Entertainment and Music
Top 10 Most Searched Differences Most Searched in Business and Finance
England vs London
Geography vs Geology
Band vs Orchestra
Complex vs Complicated


thank u for giving this information it is used for understanding the chapter.now i can answer for any question

I don't get it that concave mirrors form real image while concave lenses form virtual ,is it true I don't get it?can somebody help me

Thank you for helping me out in the finals

Not bad...improve the way of presentation....

i am very happy because it help my homework

very well presented it helped me in my exams

This was so useful. Thank you!

thank you very much for providing info. for these mirrors and lenses . The info. you have provided by the way is quite good for understanding the basis or the chapter very easily with really less doubts and confusion .

Very useful I used another website tho

THANK YOU VERY MUCH. It really helped me to answer my homework :D


Add new comment

Plain text