Back in 500 AD, people began making mirrors with silver-mercury amalgams in China and Claudius Ptolemy conducted various experiments with curved polished iron mirrors. Mirrors are of two types i.e., Plane and spherical mirrors. Plane mirrors reflect images in their normal proportions, reversed from right to left while spherical mirrors can be of further two types i.e., Concave and Convex. Concave mirrors curve inward like a spoon whereas convex mirrors bulge out and distort the reflected image, making it smaller.

What is a Convex Mirror?

Convex mirrors are also popularly called the diverging mirror or fish eye mirror and are cut out from a glass sphere, and one surface is painted. Its reflective surface bulges in the direction of the source of light and have the ability to reflect all the light that falls on them in the outward direction. So, the type of image formed by these mirrors is always virtual i.e., imaginary and erect. Also, due to this property, the size of the image of the object is smaller as compared to the actual size of the object. Therefore, a convex mirror is the most appropriate mirror in those areas where large objects have to be viewed in a tiny size and this makes it easy for a person to view the image.

Working of a Convex Mirror

In a convex mirror, there is a point where light rays received from all the different directions meet and this point is referred to as the “focal point” or the focus as this helps in creating a focal beam. There is another term called “focal length” that refers to the distance between the front and the focal point of the convex mirror and is given by the formula f= R/2 where R is the radius of curvature.

A convex or curved mirror bends outward in the shape of a dome and it always forms an imaginary image. The reason behind it is that the “center of curvature” and the point of focus are both imaginary points i.e., both of these points are unable to be reached.

It implies that the type of image made by this type of mirror can’t be projected on the screen and is an upright virtual image that is relatively smaller in size than the size of the projected object.

Magnification: It is the process of extending something in appearance, not in physical size. It can be calculated by dividing the image size by the object size.

Image formation and ray Diagram

Following are the two possibilities related to the position of the object in the case of a convex mirror:

The object is located at an infinity

The object lies between the pole of the mirror and infinity,

Location of object: Infinity

When the object is at infinity, a point-sized image is formed behind the convex mirror i.e., at principal focus. The image thus formed is highly diminished, erect, and virtual.

Location of the Object: Between pole and infinity

When the object lies between infinity and the pole of a convex mirror, a diminished, virtual (imaginary), and erect image is formed between the pole and focus, i.e., behind the mirror. The image thus formed is diminished, erect, and virtual.

Properties of a Convex Mirror

Only erect and virtual (imaginary) images are produced by convex mirrors.

The smaller and upright object reflected by the mirror will be virtual.

Convex mirrors’ outer surfaces are the only ones that reflect the image of the object.

The virtual image is always displayed regardless of its distance from the mirror.

Uses of Convex Mirror

Automated Teller Machines (ATM)

Convex mirrors are kept close to the ATM i.e., automated teller machines to permit the customers to see whether some person is standing behind them. This ensures the security of the customers while they use an ATM and safety from the theft of withdrawals of cash or any other precious item.

In Mobile Phone Camera

Some mobile phones have a selfie camera built into them that aids users to capture a self-portrait shot.

In various buildings,

Convex mirrors are often used in buildings’ hallways, including stores, hospitals, schools, hotels, and apartment buildings.

IN Passenger side mirrors

They are used in the passenger side mirror on a car, and it is labeled on the mirrors that “objects in mirror are closer than they appear” to warn the driver.

In Sunglasses

Convex mirrors are used in developing a sunglass lens to reflect the sunlight away from the person who wears these glasses.

In Production Process

A convex mirror is used in the work environment at the time of the production process as it assists in viewing a product from varying angles when placed on the conveyer belt.

This way it enhances the quality of the product by getting aware of any kind of production-based faults.

In the Magnifying Glass

Two convex mirrors if placed next to each other can form a magnifying glass.

In Street Light,

It is used as a street light reflector due to its ability to spread light rays over a larger region.

Difference between concave and Convex mirror

Meaning: Concave means rounded or hollowed like the interior of a sphere or circle while Convex means rounded or curved like the exterior of a sphere or circle.

Other names: Concave mirror is also called a converging mirror while a convex mirror is a diverging mirror and also called a fish eye mirror.

Structure: The mirror coating of the concave mirror is on the outside of the spherical surface while the mirror coating of the convex mirror is on the inside of the spherical surface. Also, in concave mirrors, the center of curvature and the reflecting surface fall on the same side of the mirror whereas in convex mirrors, the center of curvature and the reflecting surface fall on the opposite side.

Position of the Focus: In a concave mirror, the Focus lies in front of the mirror, i.e., the focal length is negative while the focal length is positive in the case of a convex mirror.

Properties of Image: The image formed by a concave mirror is real, inverted, and enlarged (except when the object is placed between P (Pole) and F (Focus), where the image is virtual, erect, and enlarged) whereas the image formed by a convex mirror is virtual, diminished and erect.

Uses: Concave mirrors are used in reflecting telescopes, torchlights, shaving mirrors, etc., as they give a magnified image of the objects whereas Convex mirrors are used as side view or rear view mirrors in vehicles and street lights as they cover a wider area of view.

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