Convex vs Concave Lens – Difference and Comparison

What is Convex Lens?

Convex lenses are those that appear thinner at the corners and feel much broader in the center. These types of lens are also known as a “converging lens” because, when light passes through them, their outer curve refracts and converges the individual beams of light into a single focal point.

The distance from the lens’ optical center to the point where all rays of light converge is called the focal length, and this point is called the primary focus or focal point.

On top of producing an authentic, upside-down image, they can also produce a virtual image if the object is brought in too near the lens. These lenses concentrate a light beam, making the subject appear larger and more precise.

It is useful in treating hypermetropia.

For instance, convex lenses are used in cameras because they concentrate the light onto the subject.

What is Concave Lens?

Concave lenses are those that are narrower in the middle and wider on the sides. A concave lens is diverging because of its round, inward form, which causes the beams to bend outward and diverge.

The resulting image is virtual, compressed, and upright, making the object appear smaller and further away than it is.

Light radiates outward from a single virtual point (the main focus or focal point). Furthermore, focal length refers to the distance between the lens’s optical center to the lens’s focal point.

It is useful in treating myopia.

For instance, the side mirrors on cars and motorcycles employ concave lenses. Film projectors can also benefit from their use in spreading the image.

Difference Between Convex and Concave Lens

  1. A concave lens is distinguished from a convex lens by the fact that it causes a ray of light traveling perpendicular to its major axis to spread out and become more narrow. The light beams that hit a concave lens diverge from the lens’s main axis, while those that hit a convex lens converge.
  2. Due to the lens’s nature, light traveling through it will either focus or spread out. That’s why we call the concave lens a diverging lens and the convex lens a focusing lens.
  3. The lens of a microscope or telescope is often convex because of its magnification capabilities, while the lens of the human eye is concave. A convex lens, on the other hand, is utilized in lasers, vehicle spotlights, and door peepholes.
  4. A concave lens distorts vision such that a nearby body or object looks much smaller and more distant than it actually is. When anything is placed next to a convex lens, however, it gives the impression that it is closer and has more volume than it actually does.

Comparison Between Convex and Concave Lens

Parameter of ComparisonConcave LensConvex Lens
As knownThe term “Diverging lens” is used to describe a concave lens.  The term “Converging lens” is used to describe a convex lens.  
The shape of the optical surfaceA concave lens has a thin middle and thicker edges.  When it comes to convex lenses, the thickest part of the glass is located in the middle, while the thinnest parts are towards the corners.  
The polarity of the focal lengthIt is sometimes referred to as a negative lens because of its negative focal length.  It is sometimes referred to as a positive lens because of its positive focal length.  
The type of image formedConstantly creates a perfect, virtual image.  Usually, it creates a real and inverse image.  
ViewMiniature and more distant than the real thing.  Larger and closer than the real thing.  

References

  1. Goldberg, F. M., & McDermott, L. C. (1987). An investigation of student understanding of the real image formed by a converging lens or concave mirror. American Journal of Physics55(2), 108-119.
  2. Tural, G. (2015). Cross-Grade Comparison of Students’ Conceptual Understanding with Lenses in Geometric Optics. Science Education International26(3), 325-343.