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Uses of Convex Lens

Last updated date: 29th May 2024
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Types and Uses of Convex Lens - Plano Convex and Biconvex Lens

A lens that is narrow at the sides and thicker at the center is called a convex lens. A convex lens converges the incoming light rays to a particular point. A Convex Lens is the source of a scientific phenomenon. As the light approaches the lens, the rays are parallel. The outermost rays refract the most. This is just the opposite when a  divergent lens known as concave, biconcave, or plano-concave, is employed.

Lenses are classified by the curving of the two optical surfaces. When the surfaces have the same radius of curvature, the lens is known as a quasiconvex biconvex.

Types of Convex Lens:

There are three types of lenses, namely the plano-convex lens, the convex lens, and finally, the concave-convex lens.

  • First, the plano-convex lens turns outward from one side to the other. Elements of good focal length have a round face and a single flat surface. The design of these lenses is unlimited use of the same light in non-sensitive applications. 

  • After that, we have a double convex lens in which the surfaces might have any  values for the two radii of curvature of the two surfaces 

  • Finally, we have a concave-convex lens that turns inward from one side and outward from the other side. 

1. Biconvex


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2. Plano-Convex

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Brief History of Lenses

Optics features a long history once it involves physics and area exploration. Galileo (1564-1642) was one of the scientists of the early days to use a tiny low telescope using a convex lens to look at the moon and alternative objects within the night sky.

Mostly telescopes and special optical instruments like spectrometers enabled folks to reveal several secrets of the universe today. All these optical instruments used for magnification essentially have one or more convex lenses.

Uses of the lens

  1. The lens is employed in microscopes and magnifying glasses to converge all the incoming light rays to a specific point

  2. The lens is used as a lens system in cameras as they focus light rays for a clear image

  3. Lens has medical purposes as well, like the correction of hyperopia

  4. It is used in a projector

  5. Plano-convex lens is used in a telescope

  6. It is a primary concentrator for multi-junction solar cells

Uses of convex lenses

A convex lens is employed in microscopes and magnifying glasses to converge all incoming light rays to a particular point. Magnification is defined as the increase in the size of the appearance of an object or another word, an enlarged once employing a lens system, the magnification of AN object is given as M= - where M is that the magnification, Di is that the distance of the image and Do is the distance of the object from the lens. 

In the given diagram, Light rays from the article enter the lens in parallel, however, they get refracted by the lens and converge as they exit, and build a "virtual image" on the membrane of your eye. This image seems to be larger than the article itself due to basic geometry: Your eyes trace the rays back in straight lines to the reflection, which is farther from your eyes than the article is.

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The convex lens is used in cameras. A camera consists of 3 main elements.

  • The body is lightweight and tight and contains all the mechanical elements.

  • The lens could be a convex one (converging lens).

  • The film or a charged couple device within the case of a photographic camera.

The rays of sunshine from the person are converged by the lens system forming a picture on the film or charged couple device within the case of an analog or digital photographic camera respectively.

The angle at which the rays enter the lens depends on the gap of the item from the lens. If the item is near to the lens the light rays enter at a sharp angle. This ends up in the rays converging far from the lens because the lens will solely bend the sunshine to an exact point that the image has to be focused on to make the film. This can be achieved by moving the lens far from the film.

Similarly, if the item is far from the lens the rays enter at a wider angle. This ends up in the rays being refracted at a trickster angle and also the image forming nearer to the lens. During this case, the lens has to be positioned nearer to the film to induce a sharp focus image.

Thus the real image of a closer object will be formed further away from the lens than the real image of a distant object and the action of focusing is the movement of the lens to generate the real image to fall on the film or charged coupled device.

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A convex lens is used for the correction of hyperopia. Farsightedness or hypermetropia is the inability to see distant objects very well, along with having difficulty in focusing on objects that are up close. However, the power to look at close objects needs a unique lens form - a form that the farsighted eye is unable to assume. Later, the farsighted eye is unable to specialize in close objects. 

The matter most often arises throughout the latter stages in life, as a result of the weakening of the ciliary muscles and/or the reduced flexibility of the lens. These 2 potential causes end up in the result that the lens of the attention will not assume the high curvature that's needed to look at close objects. 

The lens' power to refract lightweight has diminished and therefore the pictures of close objects are unit centered at a location behind the membrane. On the retinal surface, wherever the light-detecting nerve cells area unit is placed, the image isn't centered. These nerve cells find a hazy image of close objects.

The cure for the farsighted eye centers around aiding the lens in refracting the light rays. Thus, the farsighted eye is motor-assisted by the utilization of a convex lens. This convex lens can refract the light beam before it enters the attention and later decreases the image distance. By starting the refraction method before lightweight reaching the attention, the image of close objects is once more centered upon the retinal surface.

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The converging lens is used in the projector as well. A projector is employed to produce a magnified, real and inverted image of an object just beyond the focal length of a thin convex lens, and the image so formed can be projected onto a screen.

  • The image formed here is laterally and vertically inverted. Hence, the transparency has  to be in a way that is placed left to right and in an upside-down position. Thus, the image we get to see on the screen is a rectified one.

  • The transparency is placed at the focus or the focal point of the lens.

A plano-convex lens is often employed in a telescope wherever each beam comes back in and also the beam going out square is made parallel. If the lenses are positioned properly this may turn out less deviation than a bi-convex lens. During this case, the correct orientation is to have the curved surfaces of the lens pointing out towards the parallel beams.

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A convex lens can be used as a primary concentrator for multi-junction solar cells. A concentrator optical device was designed for a multi-junction electric cell, CDO-100-C3MJ. For further advancement, a lens was added above the Fresnel lens to boost the output power of the setup and cut back the requirement for the employment of solar trackers. 

The lens setup was tested with the lens setup over a 3-day photoperiod by measurement the voltage, current, irradiance, and temperature at each hour. The results showed that the lens setup created 1.94% additional power, however solely at around noon. The rise in power is because of the lens that focuses on a bigger quantity of irradiance on the electric cell over the day.

A Brief List of Uses of Convex Lens, Plano Convex, and Biconvex Lens:

There are different uses of this Lens which are described as under:

Use of Convex Lens: 

  • It is used in Magnifying Glass.

  • Can be used in the Spyhole of doors.

  • It is used in Microscopes to generate extremely magnified images of very small objects. 

  • It is also widely used in camera lenses which not only focus on the image but also magnify the image.

Use of Plano Convex: 

Plano Convex Lens can be used in many different optical systems such as magnifiers, telescopes, collimators, condensers, and imaging instruments.

Use of Biconvex Lens:

  • Biconvex Lens is used as burning glasses.

  • Biconvex Lens has many uses in real life like magnifying/condensing lenses and magnifiers.


This is a concise introduction to lenses, their different types, and their uses. In this article, we have learned how many types of convex lenses are there and how they are used in real life. Focus on the explanation of the function of such lenses along with the provided images and understand the concept well. 

FAQs on Uses of Convex Lens

1. What is the difference between Convex Lens and Convex Mirror?

The difference between a convex mirror and a convex lens is A convex mirror is opaque but a  convex lens is transparent. A convex mirror causes reflection of light but the convex lens causes refraction of light. A convex mirror forms virtual, diminished, and erect images for all positions of the object, but a convex lens can form both real, inverted images of various sizes and virtual, erect, and enlarged images depending on the position of the object.

2. What is the significance of Plano Convex Lens?

Plano-convex lenses are always positive focal length elements that have one spherical surface and one flat surface. These lenses are designed mainly for infinite conjugate (parallel light) use or simple imaging in non-critical applications. These optic lenses are ideal for all-purpose focusing elements.

3. What are the properties of Biconvex Lens?

Following are the properties of Biconvex Lens:

  • The biconvex lens has a positive focal length.

  • Their focal length is short.

  • With a conjugate ratio equal to unity, they can reduce spherical aberration while also canceling coma and distortion.

  • Biconvex lenses are symmetrical in appearance, with identical radii on both sides. They’re generally recommended for virtual imaging in the case of real objects, as well as for a positive conjugate ratio of 0.2 to 5.

4. How do you measure the focal length of the eye?

In the compound lens of the human eye, about 40 diopters come from the front surface of the cornea, the rest from the variable focus (crystalline) lens. Using this information we can calculate the focal length of the human eye, as 1/Diopter, which means 1/59=16.9 and 1/60 = 16.66, or roughly 17mm.

5. Why does a convex lens converge on light rays?

This is with the geometry of the lens curvature. Snell’s law shows that when light travels from a medium of the lower index to a higher index of refraction, the light refracts toward the “normal”. This will explain why a convex lens would “focus”; light essentially refracts towards the normal, which has the same effect as focusing toward the geometrical central axis of the lens.