Concave and Convex Mirrors - Overview, Structure, Properties & Uses

Concave and Convex Mirrors

Edited By Vishal kumar | Updated on Jul 02, 2025 04:25 PM IST

What is a Mirror?

A mirror is a reflective surface that reflects the light coming from an object and thus forms an image either real or virtual. Whenever an object is placed in front of a mirror, light coming from every part of the object falls on the mirror and gets reflected from the reflective surface and on the points where all the reflected light rays get intersected with each other, it forms an image of the same object which can be seen in the mirror.

This Story also Contains

What is a Mirror?
Types of Mirrors
Concave Mirror Definition, Properties
Convex Mirror: Definition, Properties.

Concave and Convex Mirrors

A real image is one when the reflected rays of light from the mirror intersect in actual places and thus these intersection points in space form the complete image of the object, whereas A virtual image is one when the reflected rays of light don’t intersect in actual places but we choose the points in space where these rays will meet apparently.

Types of Mirrors

Plane Mirror
Spherical Mirror

A plane mirror is one whose reflecting surface is flat and smooth and a plane mirror always forms a virtual image of all objects kept in front of the mirror and images formed by a plane mirror are virtual, and of the same size as the object.

Those types of mirror whose reflecting surface is curved are known as spherical mirrors. Spherical mirrors are generally made by cutting a sphere in two parts which results in two curved surfaces and when one side of the curved surface is polished, it acts as a spherical mirror. Spherical mirrors are generally of two kinds: Concave mirror and Convex mirror.

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Now, we will discuss Concave mirrors and convex mirrors in detail and image formation by these mirrors in each different position of an object.

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Concave Mirror Definition, Properties

What is a concave mirror and give concave mirror examples.

If we cut a hollow sphere into two parts and then if we paint the outer surface of the cut part then it behaves as a mirror whose reflecting surface is bent inwards and such types of mirrors are known as Concave mirrors.

Properties of Concave Mirror:

Light coming from infinity parallel to the principal axes converges at a point after the reflection which is called the focus of the concave mirror and thus the Concave mirror is also called the Converging mirror.
When an object is placed between the Focus and Pole of the concave mirror, it forms a virtual image which is the only case when a concave mirror produces virtual image otherwise always produces a real image.
If an object is placed at focus on the principal axes of the concave mirror, it will produce an image at infinity of very large size.

concave mirror

Convex Mirror: Definition, Properties.

What is a convex mirror?

If we cut a hollow sphere into two parts and then if we paint the inner surface of the cut part then it behaves as a mirror whose reflecting surface is bent outwards and such types of mirrors are known as Convex mirrors.

convex mirror

(Source: Geogebra)

Properties of Convex Mirror:

Light coming from the infinity parallel to principal axes will diverge after reflection thus Convex mirror is also known as a Diverging mirror.
A convex mirror always produces a virtual and erect image whatever be the position of the object.
The convex mirror forms the very small-sized convex mirror image of an object only once if the object is placed at infinity and the image is formed at the focus of the convex mirror.

Rules for Ray diagrams for concave and convex mirrors.

Any light ray coming parallel to the principal axes will pass through the focus of the concave mirror and convex mirror.
Any light ray striking the pole of the concave mirror and a convex mirror at any angle will get reflected with the same amount of angle.
Any light ray passing through the focus of the concave mirror or convex mirror, will reflect from the mirrors in a direction parallel to the principal axes.
Any light ray passing through the Centre of curvature of the concave or convex mirror, will reflect back to the same path along the center of curvature of the mirrors.

Image Formation By Concave mirrors at different locations:

There are 6 cases of concave mirrors where objects can be placed and different locations of images can be seen, they are listed as:

When the object is at infinity
When the object lies between the Focus and the Pole of the mirror.
When an object is located between Focus and Centre of curvature.
When the object lies at Focus.
When an object lies at the center of curvature
When an object lies beyond the center of curvature

Various Image formation by a concave mirror is shown by using convex mirror ray diagram rules as:

Here, the notions are named as O represents Object position, I represents image position, P represents Pole, F represents Focus, C represents Centre of curvature.

Image Formation by the concave mirror when the object lies at infinity. The image formed is real and has a very small size and formed at the focus of the concave mirror.

Image formed at infinity

When an object lies between the Focus and the pole. The image formed is virtual and erect and has a size larger than the object.

object lies between the Focus and pole

When the object lies between the Focus and the center of curvature. The image formed is Real and inverted and has a size larger than the object.

object lies between Focus and center of curvature

When the object lies at Focus. The image formed is at infinity and the image is real and much larger than the size of the object.

object lies at Focus

When the object lies at the Centre of curvature. Image formed is real and inverted and has the same size as that of the object.

object lies at the Centre of curvature

When an object lies beyond the center of curvature. The image formed is real and inverted and has a small size to that of the object and lies between focus and center of curvature.

object lies beyond the center of curvature

Image Formation By Convex mirrors at different locations:

The nature of image formed due to convex mirrors is always virtual and erect. We have only two major cases to discuss in image formation due to convex mirrors. They are listed as:

When an object is at infinity.
When an object is placed at any finite distance from the pole of the convex mirror.

Various Image formation by a convex mirror is shown by using ray diagram rules:

When an object is at infinity. The image formed is virtual and erect with a very small size to that of the object and formed at the focus of the convex mirror.

Convex mirror object is at infinity

When an object is placed at any finite distance from the pole. The image formed is virtual and erect and will form between the pole and focus of the convex mirror but is small in size to that of the object.

object is placed at Beyond Pole

S. No	Object’s Position	Image Position	Size of Image compared to object	Nature of Image
1	At infinity	At Focus	much smaller	Real
2	Between P and F	Behind the mirror	Large	Virtual
3	Between F and C	Beyond Centre of curvature	Large	Real
4	At Focus	At infinity	much Larger	Real
5	At the Centre of curvature	At the Centre of curvature	same size	Real
6	Beyond Centre of curvature	Between Focus and Centre of curvature	small	Real

The various positions of the object and their location, the nature of image formation by a convex mirror are summarized in the table given below:

S. No	Object’s Position	Image Position	Size of image compared to the object.	Nature of image
1	At infinity	At focus	much smaller	Virtual
2	Beyond Pole at any finite distance	Between Pole and focus	small	Virtual

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Frequently Asked Questions (FAQs)

1. Which type of images are formed by concave and convex mirrors?

A concave mirror is a converging mirror and depending upon the locations of an object on principal axes of the concave mirror, It forms either a Real and inverted image or a Virtual and erect image. Virtual and erect is formed in only one condition when the object is placed between Focus and the pole of the concave mirror, otherwise always forming a real and inverted image. A convex mirror is a diverging mirror and it always forms only Virtual and erect images irrespective of the position of an object on the principal axes of a convex mirror.

2. How can you differentiate between concave and convex mirrors without actually touching them?

A concave mirror produces a real image of the object and produces an inverted and virtual image if the object is placed very close to it, so put an object in front of the mirror and observe the nature of the image if it’s real and inverted then it is a concave mirror whereas if the image is virtual at any position of the object then, the mirror is a convex mirror and convex mirror always produce a virtual and erect image of the object.

3. What is the basic difference between plane mirrors and Concave and Convex mirrors?

Plane mirrors are those mirrors whose reflecting surface is flat and smooth and plane mirrors always produce the image of the object behind the mirror at the same distance as that of object distance from mirror and image formed by a plane mirror is of the same size as that of object’s size. whereas Concave and convex mirrors are types of spherical mirrors. A concave mirror is one whose reflecting surface is bent inwards and the outer curved part is polished whereas a convex mirror is one in which the reflecting surface is bent outwards and the inner surface is polished. Plane mirrors have zero radii of curvature but concave and convex mirrors have the same definite value of their radius of curvature.

4. How does the image change as an object moves closer to a concave mirror?

As an object moves closer to a concave mirror, the image undergoes several changes:

5. Can a concave mirror ever produce a virtual image?

Yes, a concave mirror can produce a virtual image when the object is placed between the focal point and the mirror surface. In this case, the reflected rays diverge and appear to come from behind the mirror, creating an upright, enlarged virtual image. This is why concave mirrors are often used for magnification in makeup mirrors.

6. Why do dentists use concave mirrors?

Dentists use concave mirrors because they can produce magnified, upright images of teeth when held close to the mouth. The mirror is positioned between its focal point and the teeth, creating a virtual, enlarged image. This magnification allows dentists to see small details more clearly, aiding in precise dental work and examinations.

7. What is meant by the term "pole" in relation to spherical mirrors?

The pole of a spherical mirror is the center point on the mirror's reflective surface. It is where the principal axis (an imaginary line perpendicular to the mirror surface) intersects the mirror. The pole is an important reference point for describing the geometry of the mirror and for constructing ray diagrams to determine image formation.

8. How does the sign convention work for mirror equations?

The sign convention for mirror equations helps determine the nature and position of images:

9. What is the main difference between concave and convex mirrors?

The main difference lies in their shape and how they reflect light. A concave mirror curves inward like the inside of a spoon, focusing light rays to a point. A convex mirror bulges outward like the outside of a spoon, spreading light rays apart. This difference in shape leads to distinct image formation characteristics and applications for each type of mirror.

10. Why do objects appear upright and smaller in a convex mirror?

Objects appear upright and smaller in a convex mirror because the mirror's outward curve causes light rays to diverge upon reflection. This divergence creates a virtual image that is always upright and smaller than the object, regardless of the object's distance from the mirror. The brain interprets these reflected rays as coming from behind the mirror, resulting in the characteristic appearance.

11. Why are convex mirrors used as side-view mirrors in vehicles?

Convex mirrors are used as side-view mirrors in vehicles because they provide a wider field of view than flat mirrors. The outward curve of the mirror allows drivers to see a larger area behind and beside their vehicle, reducing blind spots. Although objects appear smaller and farther away, the increased visibility outweighs this distortion for safety purposes.

12. What is the relationship between the focal length and radius of curvature for a spherical mirror?

For a spherical mirror, the focal length (f) is exactly half of the radius of curvature (R). This relationship is expressed mathematically as f = R/2. This means that light rays parallel to the principal axis will converge (for concave mirrors) or appear to diverge (for convex mirrors) from a point halfway between the mirror's center of curvature and its vertex.

13. How does the position of the principal focus differ between concave and convex mirrors?

The principal focus of a concave mirror is located in front of the mirror, where parallel light rays converge after reflection. For a convex mirror, the principal focus is located behind the mirror, where parallel light rays appear to diverge from after reflection. This fundamental difference affects how images are formed and the types of images each mirror can produce.

14. How do concave mirrors used in telescopes differ from those used in makeup mirrors?

Concave mirrors used in telescopes and makeup mirrors differ in their curvature and intended use:

15. What is the difference between a real and a virtual image?

A real image is formed when light rays actually converge at a point in space. It can be projected onto a screen and is always inverted. Real images are formed by concave mirrors (under certain conditions) and converging lenses. A virtual image, on the other hand, is formed when light rays appear to diverge from a point but do not actually pass through it. Virtual images cannot be projected onto a screen but can be seen by an observer. They are always upright and are formed by convex mirrors, plane mirrors, and diverging lenses.

16. How does the field of view compare between concave and convex mirrors?

The field of view differs significantly between concave and convex mirrors:

17. Can a convex mirror ever produce a real image?

No, a convex mirror cannot produce a real image. All images formed by a convex mirror are virtual, upright, and smaller than the object. This is because the reflected light rays always diverge after reflection, never converging to form a real image. The brain interprets these diverging rays as coming from a virtual image behind the mirror.

18. What is spherical aberration, and how does it affect image quality in concave mirrors?

Spherical aberration is an optical defect that occurs in spherical mirrors where light rays reflecting from different parts of the mirror do not converge to a single focal point. This results in a slightly blurred or distorted image. It affects image quality in concave mirrors, especially for objects far from the axis or when using mirrors with a large aperture. To minimize this effect, parabolic mirrors are often used in applications requiring high precision, such as telescopes.

19. What is the significance of the principal axis in spherical mirrors?

The principal axis in spherical mirrors is significant because:

20. How do concave mirrors used in solar cookers concentrate sunlight?

Concave mirrors in solar cookers concentrate sunlight by:

21. How does the focal length of a spherical mirror relate to its ability to form images?

The focal length of a spherical mirror directly affects its ability to form images:

22. How do concave mirrors create real images?

Concave mirrors create real images by reflecting and converging light rays to a point in front of the mirror. When an object is placed beyond the focal point, the reflected rays intersect at a point in space, forming a real image. This image can be projected onto a screen because the light rays actually pass through the image point. The size and orientation of the real image depend on the object's distance from the mirror relative to its focal length.

23. Why do convex mirrors always produce virtual images?

Convex mirrors always produce virtual images because they reflect light rays in a diverging manner. Regardless of the object's position, the reflected rays spread out and never converge to a real focal point. Instead, these diverging rays appear to originate from a point behind the mirror, creating a virtual image that cannot be projected onto a screen but can be seen by an observer.

24. How does the magnification of an image change as an object moves closer to a concave mirror?

As an object moves closer to a concave mirror, the magnification changes as follows:

25. Why do objects appear farther away in a convex mirror than they actually are?

Objects appear farther away in a convex mirror because the mirror's outward curve causes light rays to diverge upon reflection. This divergence creates a virtual image that is smaller than the object and appears to be located behind the mirror surface. Our brain interprets this smaller image as being farther away, based on our experience with how objects appear smaller as they move farther from us in real life.

26. How does the radius of curvature affect the focal length of a spherical mirror?

The radius of curvature directly affects the focal length of a spherical mirror. The relationship is given by the formula: f = R/2, where f is the focal length and R is the radius of curvature. This means that:

27. Can a convex mirror ever form an image larger than the object?

No, a convex mirror cannot form an image larger than the object. Regardless of the object's position, the image formed by a convex mirror is always virtual, upright, and smaller than the object. This is because the diverging nature of the reflected rays from a convex surface always results in a reduced image size. The magnification of a convex mirror is always less than 1, meaning the image is always diminished.

28. How do you determine if an image formed by a concave mirror is real or virtual using a ray diagram?

To determine if an image formed by a concave mirror is real or virtual using a ray diagram:

29. Why does a convex mirror always produce an erect image?

A convex mirror always produces an erect (upright) image because of how it reflects light rays:

30. How does the image in a concave mirror change when half of the mirror is covered?

When half of a concave mirror is covered:

31. What is the difference between the center of curvature and the focal point of a spherical mirror?

The center of curvature and focal point of a spherical mirror are distinct points:

32. Why do concave mirrors form inverted images for distant objects?

Concave mirrors form inverted images for distant objects because:

33. How does the image change in a convex mirror as an object moves farther away?

As an object moves farther away from a convex mirror: