In this article, you will learn about the concave and convex mirror, but before going forward with the concept of spherical mirrors, let us first understand the mirrors.

 

What is a Mirror? A mirror is basically a shiny polished object which reflects most of the light falling on it. To make one side reflective, the other side is polished with a particular kind of material.

 

Types of Mirror: Before learning about the concave and convex mirror, you must learn about different the two main types of mirrors:

 

1. Plane Mirror: A mirror that has a flat or plane reflective surface.

 

2. Spherical Mirror: Mirrors that have curved reflecting surfaces are known as spherical mirrors. A Spherical mirror is formed when you cut out a piece from a sphere and make either of the surfaces reflective.

 

Spherical Mirror Terms

 

Understanding ray diagrams will become easier if you learn more about terms used in ray diagram and image formed by concave and convex mirror.

 

 

1. Pole: It is the midpoint of a spherical mirror. It is represented by the letter �P�.

 

2. Centre of Curvature: It is the center of the sphere of which the mirror is a part. The center of curvature is denoted by �C�.

 

3. The radius of Curvature: It is the distance between the pole of a spherical mirror and the center of the curvature. The radius of curvature is denoted by �R�.

 

4. Principal Axis: The straight line passing through the pole of a spherical mirror and the center of curvature.

 

5. Aperture: It is the diameter of the reflecting surface of a spherical mirror.

 

6. Focus: It is a point on the principal axis where the light rays parallel to the principal axis converge (if it is a concave mirror) or appear to diverge (if it is a convex mirror) after getting reflected from the mirror.

 

7. Focal Length: It is denoted by the letter �f�. It is the distance between the center of the mirror and the focal point of the mirror. It is the point where a parallel beam of light converges or diverges.

 

Ray formation rules for spherical mirrors

 

1. When a ray passes through the center of curvature of the spherical mirror, after reflection, it will retrace its path.

 

2. When a ray of light passes through the mirror, it will always emerge parallel to the principal axis.

 

3. A ray of light that passes through a mirror always passes through the principal focus of the mirror after reflection.

 

4. The incident rays and reflected rays always follow the law of reflection.

 

5. Any incident ray which is not parallel to the principal axis is also reflected diagonally.

 

Types of Spherical Mirror: Concave and Convex Mirror

 

In this section, we will be learning about the types of spherical mirrors, which are concave and convex mirror, we will get to know about the different uses and images formed by a concave and convex mirror. Are you ready to learn the differences between a concave and convex mirror and its usage in our daily lives?

 

Concave mirrors

 

Concave mirrors have a reflecting surface that is curved inwards. Concave mirrors are also known as converging mirrors because they converge or collect light that falls upon them to one focal point. Concave mirrors concentrate light rays and produce large and clear images and thus their application is widely known and common in our daily lives.

 

Find the different uses of a concave mirror listed below:

 

Head Mirrors
Shaving Mirrors
Solar furnaces
Headlights & torches
Reflecting telescopes
Ophthalmoscope, an optical instrument
Solar Oven
Microscopes
Dental Mirrors
Satellite Dishes

 

Characteristics of Concave Mirrors:
1. The concave mirror collects and converges the light incident on it before reflection.
2. A virtual and a magnified image is formed when you place an object very close to the concave mirror.
3. When you increase the distance between the object and the concave mirror then a real image is formed and the size of the image gets smaller.
5. Concave mirrors can form images that can be large, small, erect, or virtual.

 

Image formation by Concave Mirror

 

Learn about the different types of images formed by a concave mirror. We can obtain different types of images by changing the placement of the object from a concave mirror. The formation of the images varies when the object is placed at:

 

1. At the Infinity
2. Beyond the center of curvature
3. At the center of curvature
4. Between the center of curvature and focus
5. At the focus
6. Between the principal focus and pole

 

Define the principal focus of a concave mirror

 

A concave mirror's principal focus is a location on its principal axis where all parallel light rays will converge following reflection from the concave mirror. The rays of light arriving from an object positioned at an indefinite distance from the mirror will be parallel to the principal axis, as illustrated in the figure. The rays will converge to the focal point of the mirror, which is denoted by point F in the image, after reflection from a concave mirror.

 

At the infinity: A real, point-sized, inverted, and the highly diminished image is formed at the focus when the object is placed at the infinity.

 

 

Beyond the center of curvature: A diminished image is formed between the center of curvature and focus when the object is placed beyond or behind the center of curvature. The nature of this image formed by concave mirror is real and inverted.

 

 

At the center of curvature: Same size image is formed at the center of curvature when the object is placed at the center of curvature. The nature of this image formed by concave mirror is real and inverted.

 

 

Between the center of curvature and principal focus: An enlarged image is formed behind or beyond the center of curvature when the object is placed in between the center of curvature and principal focus. The nature of this image formed by concave mirror is real and inverted.

 

 

At the principal focus: A highly enlarged image is formed at infinity when the object is placed at the focus. The nature of this image formed by a concave mirror is real and inverted.

 

 

Between the principal focus and pole: An enlarged image is formed when the object is placed between the principal focus and pole. The nature of this image formed by concave mirror is virtual and erect.

 

 

Convex Mirror

 

The reflective surface in convex mirror is on the bulge or outer side. Whatever be the distance between the mirror and the object, the image formed by a convex mirror is always diminished, erect and virtual. Convex mirrors reflect the light incident on them and therefore convex mirrors are also known as diverging mirrors.

 

Find the different uses of a Convex mirror listed below:

 

It is used as the side view or rearview mirror of a vehicle as it gives the driver a wider view of the road but being a convex mirror it also tends to diminish the image which is why �Objects in the mirrors are closer than they appear� is written on the side mirrors.

 

They are used on roads, driveways, and alleys. They are put especially at turns to provide safety to drivers and give the visibility they need to drive safely.

 

Characteristics of Convex Mirrors

 

The light gets diverged from the reflecting surface of a convex mirror which is why it is also known as a diverging mirror.The images formed by the convex mirrors are always erect, virtual, and diminished regardless of the distance between the mirror and the object.

 

Image formation by Convex Mirror

 

Learn about the different types of images formed by a convex mirror. The convex mirror always produces virtual and erect images irrespective of the position of the object. Let�s learn the nature, position, and relative size of the image formed by convex mirrors.

 

At Infinity: Behind the mirror, a virtual, erect, highly diminished, and point size image is formed at the focus when the object is placed at infinity.

 

 

Between infinity and the Pole(P) of the mirror: Behind the mirror, a virtual, diminished, and the erect image is formed between the focus of the convex mirror and the pole when the object is placed at a limited distance from the convex mirror.

 

 

Mirror Formula and Magnification

 

Mirror Formula which is also called mirror equation, showcases the relationship between the object distance and the image distance with focal length.

 

The relationship between object distance, image distance, and focal length is defined with the help of an equation, which is: 1/v-1/u =1/f

 

In the mirror formula:

 

u: It is the distance of the object from the pole of the mirror

 

v: It is the distance of the image from the pole of the mirror

 

f: It is the distance of the principal focus from the pole or focal length

 

Magnification

 

Find the expression of magnification produced by spherical mirrors below:

 

m= Height of the image (h) / Height of the object (h�)

 

m=h/h� = v/u, magnification is also equal to the ratio of the image distance with respect to the object distance.

 

When the value of the magnification has a negative sign then that concludes the image formed is real in nature, whereas, when the value of the magnification has a positive sign then that concludes the image formed is virtual in nature.