Convex Lens - Definition, Types, Uses, FAQs

Definition of Convex Lens

A convex lens is a type of spherical lens that is thicker at the centre and thinner at the edges. It is also called a converging lens because it brings parallel rays of light together at a point called the principal focus after refraction.

When parallel light rays pass through a convex lens, they meet at the focus on the other side of the lens. A convex lens can form real and inverted images or virtual and erect images, depending on the position of the object.

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Why is a Convex Lens called a Converging lens?

Because it converges a parallel beam of light on a point called the principal focus, a convex lens is called a converging lens.

Magnification of a Convex Lens

Magnification tells us how large or small the image is compared to the object.
Formula of Magnification

$
M=\frac{h_i}{h_o}=\frac{v}{u}
$

Where:

• $\mathbf{M}=$ Magnification
• $\mathbf{h}_{\mathbf{i}}=$ Height of the image
• $\mathbf{h}_{\mathbf{o}}=$ Height of the object
• $\mathbf{v}=$ Image distance
• $\mathbf{u}=$ Object distance

Important Points

• If $\mathrm{M}>1$, the image is magnified (enlarged).
• If $\mathbf{M}<\mathbf{1}$, the image is diminished (smaller).
• If M is positive, the image is virtual and erect.
• If $M$ is negative, the image is real and inverted.

Types of Convex Lenses:

CConvex lenses come in a variety of shapes and sizes.

1. Plano-convex lens: This lens has a plano-convex shape.

It is curled outwards on one side and flat on the other. Positive focal length elements with one spherical and one flat surface are used. These lenses are made for non-critical applications that require unlimited parallel light.. It's used in pharmaceuticals, defence, and robots, among other things.

2. Double Convex lens:

From both sides, it curves outwards. The Biconvex lens, or just convex, is another name for it. Plano-convex lenses of identical diameter and surface radius have a lower focal length. Longer focal lengths are required by so many optical devices. As a result, double convex lenses are chosen. It is used in projectors, monoculars, telescopes, and cameras, among other things. It served as a virtual image for the human eye and a real image for photography, as well as an optical sensor and a burner for glass.

3. Concave-Convex lenses:

From one side, it curves inwards, while from the other, it curves outwards. It can be used to compensate for other lenses' spherical aberrations. Its purpose is to control the laser beam. A concave-convex lens or meniscus is a combination of lenses with one convex lens along with one concave lens side.

Image Formation by a Convex Lens

1. The real image is produced by the convex lens at the focus when an object is positioned at infinity. The image is a fraction of the size of the actual object.
2. The real image is produced by the convex lens, between the center of curvature and the focus when an object is positioned behind the centre of curvature. When compared to the size of the thing, the image is the same size.
3. The real picture of an object is produced by the convex lens at the other center of curvature when it is at the center of curvature. When compared to the size of the object, the image is the same size.
4. When an object is placed between the center of curvature and the focus of the convex lens then, the real image is created behind it. The image is much larger than the size object.
5. A real image is produced at infinity when an object is put at the focus of the convex lens. The image is much larger than the actual object.
6. A virtual image is produced when an object is placed between the focus and the pole of the convex lens. The image is significantly larger than the actual object.

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Convex Lens: Real Image and Virtual Image

Real Image:

When an object is positioned at a distance of more than one focal length from the lens, a convex lens can be utilised to provide a genuine/real image. It can be projected in front of the lens and captured on a screen. It's what you'd find in a movie theatre, along with a projector and other equipment.

Imaginary Image:

If the item is in front of the focal point, a convex lens will produce a virtual picture. It is utilised to provide crisp images in eyewear.

Uses of Convex lenses

1. For hyperopia correction, a convex lens is used. Farsightedness, also known as hypermetropy, is the inability to see distant objects clearly while also having difficulty focusing on close objects.
2. In microscopes and magnifying glasses, a convex lens converges all incoming light rays to a single point.
3. In camera systems, the convex lens is used. Because it focuses light and generates a clear and crisp image, it is utilised in cameras.
4. The projector also uses a convex lens, also called a converging lens. A projector is used to create an enlarged, real, and inverted image of an item that is slightly beyond the focus length of a thin convex lens and can be projected onto a screen.
5. A magnifying glass is one of the most straightforward and simplest uses of a convex lens. When light rays enter the magnifying glass's convex lens, they focus on a certain focal point in front of the lens's center.

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