Difference Between Concave and Convex Lens

Difference Between Concave and Convex Lens
Difference Between Concave and Convex Lens

We will discuss here the difference between concave and convex lenses. But before that, let’s understand the main keywords related to these lenses. Also, we will learn about the types of lenses, and different types of images formed by these lenses.

These are the main keyword terms related to the lenses.

Refraction of Light

When the ray of light enters from one medium to another, it deviates from its original path. This bending of the light ray is called refraction of light.

Observe the figure below:

Concave and Convex mirror for class 7 - Refraction Of Light

Understanding the above figure

Incident ray – the ray of light falling to the surface of another medium.

Angle of incident – the angle made between the incident ray and the normal at the point of incident. 

Normal – It is a line drawn perpendicular to the surface of the other medium at the point of intersection of the incident ray.

Medium 1 – the medium in which the incident ray travels.

Medium 2 – the medium in which the incident ray enters (the medium in which refracted ray travels).

Refracted ray – The incident ray gets diverted from its original path after entering into another medium. This diverted ray is called a refracted ray.

Angle of refraction – the angle made between the refracted ray and the normal at the point of incident in the second medium.

The light ray bends towards or away from the normal after entering the second medium. The bending of the incident ray depends upon the type of medium it is entering into.

It bends towards the normal if the medium it is entering into (medium 2) is denser than the medium it is initially travelling (medium 1). Similarly, it bends away from normal if medium 2 is rarer than medium 1.

Center Of Curvature

The spherical surfaces of the lens are the parts of a sphere. The centre of this sphere is called the center of curvature.

Concave and Convex lens for class 7 - parts of a lens

Principal Axis

It is the straight line passing through the center of curvatures and the poles.

Pole

The centers of the spherical surfaces are called the pole.

Focus

Focus is the point where all the incident rays appear to meet after reflection. It is always on the principal axis and for the small curvature lens and mirrors it is equal to half of the radius of the spheres.i.e:-

F= R/2

Types Of Images

There are normally four types of images.

1. Real Image

2. Virtual Image

3. Erect, and

4. Inverted Image

Read their definitions in detail Concave and Convex Mirrors

Definition of Lens

Lens are the parts of two concave or convex spherical mirrors as shown in the image above. Lenses are made of transparent material and allow light to pass through them.

The light is refracted after entering into the lenses as the medium of the travel of a light ray changes from the air to the glass.

Types of Lens

There are mainly two types of lenses. They are:- 

1. Concave Lens

2. Plano-concave Lens

3. Diverging Meniscus

4. Convex Lens

5. Plano-Convex Lens

6. Converging Meniscus

Here we will discuss about the Concave and Convex Lenses only.

Difference between Concave and Convex Lens: Definitions

Concave Lens

Bound by two spherical surfaces this lens is thinner at the center and thicker at the edges. Concave lenses are also called diverging lenses.

Concave and Convex lens for class 7 - Concave Lens

Note:- The image formed in the case of the concave lens is similar to that of the convex mirror.

Uses of Concave Lens

Concave lenses are used in spectacles, binocular, telescopes, and in photography.

Convex Lens

Bound by two spherical surfaces, this lens is thicker at the center and thinner at the edges. Convex lenses are also called converging lenses.

Convex Lens - difference between concave and convex lens

Note:- The images formed in the case of the convex lens are similar to that of the concave mirror.

Uses of Convex Lens

Convex lenses are used for microscopes and magnifying glasses, and as camera lenses.

Difference Between Concave and Convex Lens : Table

Concave LensConvex Lens
They are thick at the edges and thin at the center.They are thin at the center and thick at the edges.
Only the virtual image can be formed.The real, as well as virtual image, can be formed.
Erect and small-sized images are formed.An erect, inverted, small, as well as magnified, images, can be formed as per the distance of the object from the mirror.
They are called diverging lenses.They are called converging lenses.
Used to correct short-sightedness or myopia.Used to correct long-sightedness or hypermetropia.

Take the Quiz

The quiz contains the questions related to the refraction, reflection and lenses.

Aiye Samjhein - Reflection Quiz

Welcome to Quiz – Reflection, refraction and lenses

Date – October 20, 2020

Time05 Minutes

Click “Next” to start the quiz


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