Uses of Convex Lens and Its Application

Edited By Vishal kumar | Updated on Jul 02, 2025 04:48 PM IST

When the light passes through a lens and the emergent rays are converging in nature then that type of lens is known as converging lens or convex lens.

There are three types of convex lens

Bi-convex or double convex lens
Plano convex lens
Concavo convex lens

In convex lens light rays get converged or come closer to each other as in the diagram above. Due to this property, convex lenses are used in different ways in different objects.

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Application of convex lens/use of lens/what are the uses of lenses/state two uses of convex lens/uses of lenses in our daily life:

Magnifying glass uses convex lenses .
Eyeglasses use convex lenses.
Camera uses a convex lens.
Telescopes use convex lenses .
Microscopes use convex lenses.

Convex lens used in magnifying glass:

Convex lens used in magnifying glass

Magnifying glasses are most commonly used for seeing things larger. The light from the object comes through the convex lens of the magnifying glass .The light gets converged due to the convex lens and makes the image larger in our eyes.

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Convex lens used in eyeglasses:

Convex lens used in eyeglasses

In hyperopia a human cannot be able to see things away from his sight. So, when the light rays come from an object and get through a lens then the image is formed in the retina and the farsightedness patient sees the object without any difficulty.

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Convex lens used in camera:

Convex lens used in camera

Image of convex camera

Convex lens is used in cameras not just for its focusing quality but also for its magnifying quality. Camera uses both the lenses convex and concave . There are convex lenses followed by a concave lens then a convex lens in a camera.

Convex lens used in Telescopes :

Convex lens used in Telescopes

Convex lens used in Microscope:

Convex lens used in Microscope

There are two convex lenses in a microscope. The light rays from the object come through the objective lens then through the eyepiece .Due to double refraction the object becomes larger than the actual size of the object , So, the small objects also get magnified .

Note: Magnifying glass meaning in telugu is భూతద్దం
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NCERT Physics Notes:

Frequently Asked Questions (FAQs)

1. What is the other name of convex lens?

The other name of convex lens is converging lens.

2. What happens when light rays emerge from a convex lens?

When light rays emerge from the convex lens the rays converge on the focus point.

3. Name a few types of convex lens.

Bi-convex lens , plano-convex lens and concave-convex lens are a few types of convex lens.

4. What is an equi-convex lens?

If the radius of curvature equals that type of convex lens is known as equi-convex lens.

5. What is a convex lens?

The lens which converges the rays of light are known as convex lenses.

6. Which lens is used in a camera?

Convex lens

7. Is a microscope lens concave or convex?

Convex lens

8. Which lens is used in spectacles?

Spectacles use both concave and convex lenses.

9. What are the spherical lens uses?

They are used in imaging applications.

10. What is convex lens magnifying glass?

A convex lens that makes an object appear bigger than the actual is called a magnifying glass.

11. What is the other name of convex lens?

The other name of convex lens is converging lens.

12. What happens when light rays emerge from a convex lens?

When light rays emerge from the convex lens the rays converge on the focus point.

13. Name a few types of convex lens.

Bi-convex lens , plano-convex lens and concave-convex lens are a few types of convex lens.

14. What is an equi-convex lens?

If the radius of curvature equals that type of convex lens is known as equi-convex lens.

15. What is a convex lens?

The lens which converges the rays of light are known as convex lenses.

16. Which lens is used in a camera?

Convex lens

17. Is a microscope lens concave or convex?

Convex lens

18. Which lens is used in spectacles?

Spectacles use both concave and convex lenses.

19. What are the spherical lens uses?

They are used in imaging applications.

20. What is convex lens magnifying glass?

A convex lens that makes an object appear bigger than the actual is called a magnifying glass.

21. What is a convex lens and how does it affect light rays?

A convex lens is a transparent optical device that is thicker in the middle than at the edges. It causes parallel light rays to converge to a single point called the focal point. This happens because the curved surface of the lens refracts (bends) light rays inward as they pass through.

22. Why is a convex lens also called a converging lens?

A convex lens is called a converging lens because it causes parallel light rays to come together (converge) at a single point after passing through the lens. This convergence point is known as the focal point of the lens.

23. What is the focal length of a convex lens and how is it determined?

The focal length of a convex lens is the distance from the center of the lens to the focal point. It is determined by the curvature of the lens surfaces and the refractive index of the lens material. A more curved lens or a higher refractive index results in a shorter focal length.

24. How does the image formation change as an object moves closer to a convex lens?

As an object moves closer to a convex lens, the image formation changes as follows:

25. What is the difference between real and virtual images formed by a convex lens?

A real image is formed when light rays actually converge at a point after passing through the lens. It can be projected on a screen. A virtual image is formed when light rays appear to diverge from a point but don't actually meet there. Virtual images cannot be projected on a screen but can be seen when looking through the lens.

26. How does a convex lens function in a magnifying glass?

In a magnifying glass, a convex lens is used to create an enlarged, virtual image of a nearby object. When the object is placed within the focal length of the lens, the light rays diverge after passing through the lens, creating an upright, magnified virtual image that appears to be behind the object.

27. Why are convex lenses used in cameras?

Convex lenses are used in cameras to focus light from the scene onto the image sensor or film. The lens converges light rays to form a real, inverted image of the scene. By adjusting the distance between the lens and the sensor (focusing), the camera can create sharp images of objects at different distances.

28. How do convex lenses help correct farsightedness (hyperopia)?

Convex lenses help correct farsightedness by converging light rays before they enter the eye. In a farsighted eye, light focuses behind the retina. The convex lens brings the focal point forward onto the retina, allowing clear vision of nearby objects.

29. What is the role of a convex lens in a telescope?

In a refracting telescope, the convex lens serves as the objective lens. It collects light from distant objects and forms a real, inverted image at its focal point. This image is then magnified by the eyepiece (another lens) for viewing. The large diameter of the objective lens allows it to gather more light, making faint objects visible.

30. How does a convex lens create a projector image?

In a projector, a convex lens is used to create a large, real image on a screen. The object (e.g., a slide or digital display) is placed just beyond the focal point of the lens. This causes the lens to form an enlarged, real, inverted image on the screen. The distance between the lens and screen is adjusted to focus the image.

31. What is chromatic aberration in convex lenses and why does it occur?

Chromatic aberration is a distortion where different colors of light are focused at slightly different points by a convex lens. It occurs because the refractive index of the lens material varies with the wavelength of light. This causes the lens to bend different colors of light by different amounts, leading to colored fringes around images.

32. How do convex lenses function in microscopes?

In a compound microscope, two convex lenses work together:

33. What is the thin lens equation and how is it used with convex lenses?

The thin lens equation is 1/f = 1/u + 1/v, where f is the focal length, u is the object distance, and v is the image distance. This equation relates the position of the object and image to the focal length of the lens. It's used to calculate unknown variables when two of the three are known, helping predict image formation for convex lenses.

34. How does the power of a convex lens relate to its focal length?

The power of a convex lens is inversely proportional to its focal length. It's measured in diopters (D) and calculated as P = 1/f, where f is the focal length in meters. A lens with a shorter focal length has a higher power and bends light more strongly. For example, a lens with a focal length of 0.5 m has a power of 2 D.

35. What is the difference between a converging lens and a diverging lens?

A converging lens (convex) causes parallel light rays to come together at a focal point after passing through it. It can form both real and virtual images. A diverging lens (concave) causes parallel light rays to spread out after passing through it. It only forms virtual images and is used to correct nearsightedness.

36. How do convex lenses help in correcting astigmatism?

Convex lenses alone don't correct astigmatism, which is caused by an irregularly shaped cornea. However, convex cylindrical lenses or toric lenses (which have different curvatures in different meridians) can be used in combination with spherical lenses to correct both astigmatism and farsightedness or nearsightedness simultaneously.

37. What is the significance of the center of curvature in a convex lens?

The center of curvature is the center of the sphere that would form if the curved surface of the lens were extended into a complete sphere. It's significant because light rays passing through the center of curvature are not refracted (bent) by the lens. This property is useful in ray diagrams and understanding image formation.

38. How does the thickness of a convex lens affect its focal length?

Generally, increasing the thickness of a convex lens while keeping its surface curvature constant will decrease its focal length. This is because thicker lenses bend light more, causing rays to converge more quickly. However, very thick lenses may introduce additional aberrations, so there's a practical limit to this effect.

39. What is the principle behind using convex lenses in lighthouses?

Lighthouses use large convex lenses (often Fresnel lenses) to collimate light from a bright source into a narrow, powerful beam. The lens takes diverging light rays from the source and makes them parallel, creating a concentrated beam that can be seen from great distances. This principle allows a relatively small light source to be visible over long ranges.

40. How do convex lenses contribute to the functioning of the human eye?

The crystalline lens in the human eye is a flexible convex lens. It focuses light onto the retina, forming an inverted real image. The lens can change its shape (accommodate) to focus on objects at different distances. This ability, combined with the cornea's refraction, allows us to see clear images of both near and far objects.

41. What is the difference between a simple and a compound lens system?

A simple lens system uses a single lens to form an image, while a compound lens system uses multiple lenses in combination. Compound systems, like those in microscopes or cameras, can provide higher magnification, better image quality, and reduced aberrations compared to simple lenses. They allow for more complex optical designs and greater control over image formation.

42. How does a convex lens form a solar image, and why is this dangerous?

A convex lens can focus sunlight to a small, intense point called a solar image. This occurs because the lens converges parallel light rays from the sun to its focal point. This concentrated light can be extremely hot and potentially start fires or cause burns. It's dangerous to use convex lenses (like magnifying glasses) to focus sunlight without proper precautions.

43. What is the relationship between the object distance, image distance, and focal length in a convex lens?

The relationship is described by the lens equation: 1/f = 1/u + 1/v, where f is the focal length, u is the object distance, and v is the image distance. This equation shows that as the object moves closer to the lens (u decreases), the image moves farther away (v increases), assuming the focal length remains constant.

44. How do convex lenses help in creating holograms?

Convex lenses play a crucial role in holography by helping to control and direct laser light. They're used to expand, collimate, and focus laser beams in holographic setups. In some holographic displays, convex lenses may also be used to magnify or project the holographic image, enhancing its visibility or size.

45. What is spherical aberration in convex lenses and how can it be minimized?

Spherical aberration occurs when light rays passing through different parts of a spherical lens don't converge to a single focal point. Rays passing through the edges of the lens are focused closer to the lens than those passing through the center. This can be minimized by using aspherical lenses, which have a more complex surface curvature, or by using a combination of lenses that cancel out each other's spherical aberration.

46. How do convex lenses function in virtual reality (VR) headsets?

In VR headsets, convex lenses are used to magnify the display screen and create a wide field of view. They also help focus the image at a virtual distance, reducing eye strain. The lenses correct for distortions in the displayed image and work with software adjustments to create an immersive 3D experience.

47. What is the concept of optical center in a convex lens?

The optical center of a convex lens is a point on the principal axis through which light rays pass without any deviation. It's typically located at the geometric center of a thin, symmetrical lens. Understanding the optical center is crucial for ray diagrams and calculations involving image formation, as rays passing through this point are not refracted.

48. How does the curvature of a convex lens affect its focal length?

The curvature of a convex lens is inversely proportional to its focal length. A lens with a greater curvature (more bulged out) will have a shorter focal length and thus a higher refractive power. Conversely, a lens with less curvature will have a longer focal length and lower refractive power.

49. What is the principle behind using convex lenses in overhead projectors?

Overhead projectors use a large convex lens (often a Fresnel lens) to project an enlarged image of a transparent slide onto a screen. The slide is placed just above the focal point of the lens, causing the lens to form a real, inverted, and enlarged image on the screen. Additional lenses may be used for focusing and image correction.

50. How do convex lenses contribute to the functioning of telescopes?

In refracting telescopes, convex lenses serve two main purposes:

51. What is the concept of principal focus in a convex lens?

The principal focus (or focal point) of a convex lens is the point where parallel light rays converge after passing through the lens. There are two focal points, one on each side of the lens, equidistant from the optical center. The distance from the optical center to a focal point is the focal length. Understanding the principal focus is crucial for predicting image formation and characteristics.

52. How do convex lenses help in correcting presbyopia?

Presbyopia is an age-related condition where the eye's lens loses flexibility, making it difficult to focus on close objects. Convex lenses in reading glasses help correct this by converging light rays before they enter the eye, effectively doing the focusing work that the eye's lens can no longer do. This allows clear vision of nearby objects without straining the eye's focusing muscles.

53. What is the difference between a plano-convex and a biconvex lens?

A plano-convex lens has one flat surface and one convex surface, while a biconvex lens has two convex surfaces. Biconvex lenses generally have shorter focal lengths and higher refractive power than plano-convex lenses of similar dimensions. Plano-convex lenses are often used in applications where light needs to be focused from a collimated beam or where minimizing certain aberrations is important.

54. How does the refractive index of the material affect the properties of a convex lens?

The refractive index of the lens material directly affects its focusing power. A higher refractive index means the lens bends light more strongly, resulting in a shorter focal length for the same lens shape. This allows for thinner, lighter lenses with the same optical power, which is particularly useful in eyeglasses. However, higher refractive index materials can also introduce more chromatic aberration.

55. What is the concept of conjugate foci in convex lenses?

Conjugate foci are pairs of points in object and image space where light from one point is focused to form an image at the other point. In a convex lens, if an object is placed at one of these points, its image will form at the conjugate point. This concept is important in understanding image formation and in designing optical systems where specific object-image relationships are required.

56. How do convex lenses function in barcode scanners?

In barcode scanners, convex lenses are used to focus laser light into a narrow beam and to collect reflected light from the barcode. The lens system typically includes:

57. What is the significance of the f-number in convex lenses used in cameras?

The f-number (or f-stop) is the ratio of the lens's focal length to its aperture diameter. It's significant because:

58. How do convex lenses contribute to the functioning of fiber optic endoscopes?

In fiber optic endoscopes, tiny convex lenses are used at both ends of the fiber bundle:

59. What is the concept of cardinal points in a convex lens system?

Cardinal points are a set of reference points that describe the optical properties of a lens system. For a convex lens, key cardinal points include:

60. How do convex lenses help in creating beam expanders?

Beam expanders use a combination of convex lenses to increase the diameter of a laser beam while maintaining its collimation. Typically, they consist of:

61. What is the principle behind using convex lenses in collimators?

Collimators use convex lenses to convert diverging light rays into parallel rays. The principle is based on placing a point source of light at the focal point of the convex lens. Light rays emanating from this point will emerge parallel