Difference Between Mirror and Lens

Dhristi JEE 2022-24

Lens and Mirror Difference

The Lens is a transparent thick material (made of glass/plastic) that causes light Rays to bend in a particular way as they pass through it, be it converging the Rays to a specific point or diverging them away from the particular point.


A Mirror is an object that helps us see our Image and the Image behind us.


So, what is the difference between Lens and Mirror? Let’s observe this by the Images of these:


(Image will be Uploaded Soon)


Lens and Mirrors have differences in their Image formation. In this article, we will learn the Lens and Mirror difference.


Difference Between Lens and Mirror


Lens

Mirror

The Lens is a material made of glass or plastic bounded by two surfaces. It can either be curved at one side or both sides. 

The Mirror implies a glossy surface at one end and produces an Image of an object by reflection. 

A Mirror follows the laws of reflection.

The Lens is a transparent thick material that is shaped in such a manner that it bends the light passing through it. 

It can converge the light Rays onto a specific point or diverge it away from that point.

A Mirror is a reflector that is shiny from one side and reflects the light Rays coming from the object to make it appear as an Image to the other side.

The Lens is of two types viz: Concave Lens and convex Lens.

A Mirror is of three types viz: concave Mirror, plane Mirror, and convex Mirror

A Lens has two focal points namely F and 2F.

A plane Mirror has no focal point.

It forms an Image the same size as that of the object.

A concave Lens is a diverging Lens

A convex Lens is a converging Lens.

A concave Mirror is a converging Mirror A convex Mirror is a diverging Mirror.

Concave Lenses are used as an aid for people having Myopia or nearsightedness.

Convex Lenses are used as an aid for people having Hypermetropia or farsightedness.

Examples of Concave Mirror - shaving/make up Mirror

In streetlights and car headlights

Convex Mirror - Rearview Mirror in two and three-wheelers

The formula for the image formation by the lens is:

\[\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\]

Where,

v=the distance of image

u=the distance of object

f=focal length

The formula for the image formation by the lens is:

\[\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\]

Where,

v=the distance of image

u=the distance of object

f=focal length

Image formation for the object placed at infinity:

  1. Concave Lens

  2. Convex Lens

Sign conventions:

The Ray diagram for the object placed at infinity:

  1. Concave Mirror

  2. Convex Mirror

Image formation for the object placed at F

  1. Concave Lens

  2. Convex Lens

Image formation for the object placed at F


Image formation for the object placed between F (focus) and O (optical center)

Image formation for the object placed between F and C

Real-life example:

Whatever we observe around us is because of something called ‘Lens’. Eyes are natural Lenses that help us to read, write, watch movies, distinguish among various shades of a single color.

Real-life example:

Mirrors help us see our Image.

We use Mirrors at beauty salons, on vehicle headlights, torchlights, streetlamps, 


Difference Between Mirror and Lens

The difference between Mirror and Lens can be better understood by their sign conventions followed by their varying Image formation. Firstly, we will have a look at their sign conventions followed by the Ray diagram of objects placed at varying positions in both the Mirror and the Lens.


Sign Convention of a Mirror:

  • All the distances should be measured from the pole (P) of the Mirror. 

  • Distances that are measured in the direction of the incident Rays should be considered positive, and negative when distances are taken from the opposite side of the incident Rays.

  • If the Image is formed behind the Mirror, then the Image distance is taken positively from the pole (P) along the principal axis.

  • The height of the object is taken as positive above the principal axis and negative along the principal axis.

  • The focal length ‘f’, is positive for a concave Mirror and a convex Mirror, it is negative.


Sign Convention of the Lens:

  • All the distances should be measured from the optical center of the Lens.

  • Distances that are considered along with the direction of the incident Rays should be considered positive, and negative when distances are taken from the opposite side of the incident Rays.

  • Above the principal axis, the height is considered positive, while below the principal axis, the height is considered negative.

  • Objective distance is considered positive, the real Image distance is considered positive, and virtual Image distance is considered negative. 

  • Magnification of the real Image is considered negative and that of the virtual Image is considered positive.


THINGS TO REMEMBER IN THIS CHAPTER

  •  Concave Lenses are used in eyeglasses and contacts, flashlights, photography etc.

  • Lens formula - 1/v-1/u=1/f

  • Mirror formula - 1/v+1/u=1/f

  • Lens is transparent and it produces the Images by refraction.

  • Mirror is the glass surface and the back side of the Mirror is a silvery backing which helps to form an Image due to reflection.

  • Mirror can be plan or plan but Lens can be curved in one or two surfaces.

  • Mirror works on the principle of reflection.

  • Lens work on the principle of refraction.

  • The Mirror reflects the light falling on them.

  • Lens manipulates the light 

  • Mirrors are of two types - convex and concave.

  • Types of Lenses are of 6 types.

  • Mirror do not have a focal point in it.

  • Lenses have two focal points.

  • Mirror can be made of glass or metal.

  • Lens are made of glass or plastic.

  • Mirror forms a clear Image when an object is placed in front of it.

  • The curves of the Lenses are always spherical.

  • Lenses are used in  telescopes, microscopes etc.

  • Mirrors are used to make looking glass, home decors, projectors etc.

  • Combination of two prisms is called a Lens.

  • Mirror is a glass polished on one side and the other side is covered or coated with metal amalgam which helps to reflect and form an Image on the Mirror.


Tips to Remember While Preparing this Chapter-

  • This topic is really important in Physics. This topic is covered in the Reflection and Refraction in Class 10.

  • The concept of Mirror and Lenses are to be covered first in order to understand how they work.

  • The principle of reflection and principle of refraction is important in this chapter because the Mirror and Lens are based on these principles. Students should not confuse these principles in order to have a clear understanding how the Mirror and Lenses work.

  • Make notes and mention what the Mirror and Lenses are and then how the principles work. Here the notes are important because this will help them to remember the principles.

  • While making the notes, also draw the Lenses and the Mirror in order to have an idea how the law of reflection and refraction works when the light passes through them. While making this make sure they are correct and make the notes really simple because that will help them while preparing for examinations.

  • Make a different table for the Mirror and Lens and write what are the differences between them because this might be asked in the examination, so it is better to be prepared from the beginning. There are many differences between them so need to mention all of them and remember them.

  • This will make the students remember the topics in an easy way.

  • Always try to solve the questions given at the end of the chapters. Those are important because they can test the knowledge of how much they have understood the topics.

  • After solving  the questions, check it with your teachers or tutors in order to know the correct answers to it.

  • Students can also refer to the solution books available in the market or they can download it from Vedantu's website. They can check the answers to answer the questions correctly.

  • This chapter also has the problems in it so the students should learn the formulas of Lens and the Mirror. They are a little similar so it is easy to confuse the formulas. It is recommended to remember them without getting confused between them.

  • While solving the problems related to this topic, make the diagram in order to have an idea what the problem is asking  about and they will get an idea by having a sketch of  the diagram. They just need to follow the formulas in order to solve the problems.

  • Students can have some extra help like they can have help from their friends or parents or even they can hire a tutor to understand the chapter and they can even clear the doubts from them. Vedantu offers online classes where the students can enroll in order to have their topic cleared.

  • Students can also download the study materials related to this topic from the Website of Vedantu in PDF, they can refer to the notes while preparing for the examinations because the notes and study materials cover the topic in a very simple way so that it will be easy for the students to refer to it. The notes are made according to the latest syllabus of the topic.

FAQs on Difference Between Mirror and Lens

1.Can a Convex Lens Form an Image the Same Size as that of the Object?

Yes!

When an object is placed at a distance u = 2f from the optical center of the lens, the image formed by the convex lens will be the same size as that of the object.


2.Write Two Points on the Convex Lens?

  • A convex lens is a converging lens, so after refraction, rays coming from the distant source meet at a specific point or appear to meet at that point.

  • The image formed by the convex lens can be real, virtual, enlarged, diminished based on the position of the object.

3.Write Two Points on the Concave Lens?

  • A concave mirror is a diverging lens, so after refraction, the rays diverge at various points.

  • The nature of the image formed by a concave lens is virtual and diminished (negligible in its size).

4.Write a Few Applications of a Mirror and a Lens?

The applications of a mirror and a lens lie hereunder:

Lens

We can find lenses in microscopes, our wearing glasses, telescopes, magnifying glasses, etc.


Mirrors

We can see mirrors in automobile headlights, solar appliances, houses, etc. 


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