Convex Mirror: Properties, Image Formation, and Everyday Applications

A Convex mirror is one of the most commonly used types of mirrors in our daily lives. A convex mirror has a shiny, outward-curved surface that makes it different from a plane mirror. Have you ever noticed the curved mirrors on the sides of vehicles or in shop corners that let you see a wider view? These are convex mirrors! 

 You can spot convex mirrors in many places, such as in vehicles, hallways, and shops for safety, and even in ATMs for security. 

This article covers what a convex mirror is, how image formation by a convex mirror ray diagram, and where we use them in our daily lives. 

Table of Contents

• Understanding Convex Mirror
• Image Formation by a Convex Mirror
• Uses of Convex Mirror
• Key Terminologies of a Convex Mirror

Understanding Convex Mirror

A Mirror is a shiny, reflective surface that reflects light and produces a real or virtual image. A convex mirror is a type of spherical mirror. 

To understand this simply, let’s imagine one simple example, a hollow ball. If you paint its inside surface, the outside shiny part becomes reflective. That’s how a convex mirror is made!

Interesting, isn’t it? Its shiny surface curves outward, just like the outer side of a ball, helping it reflect light in a wider direction.

From the above, it can be concluded that the reflecting surface of spherical mirrors is considered to form a part of the surface of any sphere. In this type of mirror, the reflection takes place from the outer surface of the spherical mirror. 

In the above convex mirror ray diagram, notice how the convex mirror bulges outward and reflects light rays that spread apart after reflection, and this helps it to form a virtual, upright, and smaller image of the object.

Let’s place an object in front of the mirror to clearly understand how this image is formed.

In a convex mirror, the focal point (F) and the centre of curvature (2F) lie behind the mirror, making them imaginary points. Since reflected light rays never actually meet but only appear to meet behind the mirror, the image formed is virtual and cannot be projected on a screen.

Here is what you will observe: from a distance, the image appears small and upright. If the object moves closer to the mirror, the image becomes slightly larger and diminished. 

Let's try to understand this with a simple example.

The surface of the spoon, which bulged outward, can be assumed to be a convex mirror. It is also known as a diverging mirror, as the light after reflecting through its surface diverges in many directions but appears to meet at some points where the virtual, erect image of diminished size is formed.

This simple example helps us see how a mirror reflects light and forms images. 

Let’s now study in detail how image formation takes place in a convex mirror when the object is placed at infinity and between infinity and the Pole.

Image Formation by Convex Mirror

• When an object is placed at an infinite distancein front of a mirror, then light rays coming from the object reach the mirror almost parallel to each other. 

Incident rays reflect by following the laws of reflection. So the image formed will be a point-sized image at the principal focus, i.e., behind the mirror. The image formed is highly diminished, virtual, and erect.

• When an object is placed at a finite distancein front of a mirror between infinity and the pole, the light rays reflect by following the laws of reflection. 

Here, the reflected light ray will appear like spreading out instead of meeting in front of the mirror. An image will be formed between the pole and focus, and it will be behind the mirror, and the image will be diminished, virtual, and erect. 

Now that we know how a convex mirror forms images, let’s look at how this property is used in real life. 

Uses of a Convex Mirror in Everyday Life

• In vehicles, convex mirrors are used as side or rear-view Mirrors,  because the curved surface enables drivers to see a wide area behind and to the side. 
• Convex mirrors are used in elevators and corridors to help look around in crowded places to avoid accidents.
• In ATMs (Automatic Teller Machines), a small convex mirror is used to help users keep an eye on their surroundings for safety.
• In optical instruments like telescopes, microscopes uses convex mirrors are used to gather light over a larger area. 

Read More: Uses of a Convex Mirror

Key Terminologies of a Convex Mirror

Pole P is the midpoint of the spherical mirror.  Aperture is the point from which the reflection of light actually takes place.  The principal axisis an imaginary line that passes through the optical center and the center of curvature of a spherical mirror.  Center of curvature C is the point at the centre of the mirror surface that passes through the curve of the mirror.  The radius of curvature R is the linear distance between the pole and the center of curvature.  The principal focus is present on the axis of the mirror where the rays of light parallel to the principal axis converge after reflection.  Focus is a point on the principal axis where a light ray parallel to the principal axis will converge after reflection.

Till now, we’ve learned how a convex mirror works, how it forms images, and where we use it in our daily lives. These mirrors may seem ordinary, but they help us in many ways, from giving drivers a wider view on the road to improving safety in shops, ATMs, and buildings. Convex mirrors are a perfect example of how simple science makes life easier and safer every day.