

What Are the Types and Real-World Applications of Spherical Mirrors?
A spherical mirror is a mirror that has the shape of a piece carved out of a sphere.
A spherical mirror is categorised into two forms, namely: concave and convex. On this page, we'll learn about the following:
Type of spherical Mirrors
Application: usage, Examples
Derivations for a mirror formula with a ray diagram
Mirror images with their attributes: R, C, f, P, and Principal axis
The surfaces of most curved mirrors are shaped as spheres, although optical devices can sometimes use other shapes. For example, a plane mirror is a mirror whose reflecting surface is flat, and if the reflecting surface is curved, the mirror is called a curved mirror.
Types of a spherical mirror
There are two types of curved mirrors;
Concave mirror: Outer surface: silvery polished, inner surface: reflective
Convex mirror: Outer surface: Reflective, Inner surface: Polished Light reflected by convex and concave mirrors
Take a spoon for an example; there are two such reflecting surfaces on a spoon. These two mirrors are called spherical mirrors. The reflecting surface on both sides look like a part of a sphere, hence the name. These two are further given a notable name. The mirror that has its reflecting surface curved inwards is called a concave mirror, and the mirror that has its reflecting surface curved outwards is called a convex mirror.
Applications
Concave Mirrors are used as reflectors and converging of light. It is used as a makeup and dentists mirror, headlights for a motor vehicle etc. Convex Mirror is used in security monitors in ATMs, hospitals, hotels, schools etc. It is also used as side-view mirrors in cars.
Concave Mirror
Reflectors, Converging of light, Solar cooker, motor vehicle headlight, shaving, and makeup mirror, microscope, Telescope, Satellite dishes, dentist's mirrors.
Convex Mirror
It is used in security monitors, Side-view mirrors in cars, Security mirrors in ATMs, in buildings such as hotels, hospitals, stores, schools, etc. Key points: Consider a ray image of a Concave Mirror.
Derivation of Mirror Formula
In a mirror, the place that is the centre of the reflecting surface is called a pole. It is represented with a point P. There is also a centre in the sphere called the centre of the curvature, and the radius will be called the radius of the curvature. The line joined from the pole to the centre of the curvature is called the principal axis. The midpoint of the line segment joining the pole P and the centre of curvature C is called the focal point. It's denoted by the letter F.
f = focal length
a = The distance of the object from the pole of the mirror.
b = The distance of the image formed from the mirror.
A few patterns that are essential to understand before deriving the equation are:
Pole "P" is the place from where all distances are measured.
Distances measured in the light incidence direction are considered positive, and those taken from the opposite direction are deemed negative.
The positive and negative points can be determined by the height, if they are above the principal axis, they are supposed to be positive and when the height is lower than the principal axis are negative.
The positive and the negative image distance can be determined by the ray diagram.
FAQs on Spherical Mirrors: Complete Guide for Students
1. What is a spherical mirror, and what are its main types?
A spherical mirror is a mirror whose reflecting surface is a part of a hollow sphere. Unlike plane mirrors, their surfaces are curved. There are two primary types of spherical mirrors:
- Concave Mirror: A spherical mirror where the reflecting surface is curved inwards, towards the centre of the sphere. It is also known as a converging mirror because it converges parallel rays of light to a single point.
- Convex Mirror: A spherical mirror where the reflecting surface is curved outwards. It is also known as a diverging mirror because it causes parallel rays of light to appear to diverge from a single point behind the mirror.
2. What is the fundamental difference between a real image and a virtual image formed by a spherical mirror?
The fundamental difference lies in how the images are formed and whether they can be projected. A real image is formed when light rays actually converge and meet at a point after reflection. It is always inverted and can be captured on a screen. In contrast, a virtual image is formed when light rays appear to diverge from a point behind the mirror; they do not actually meet. A virtual image is always erect and cannot be projected onto a screen.
3. What are the essential terms used to describe a spherical mirror's geometry?
To understand how spherical mirrors work, it is important to know these key terms:
- Pole (P): The geometric centre of the spherical mirror's reflecting surface.
- Centre of Curvature (C): The centre of the hollow sphere of which the mirror is a part.
- Radius of Curvature (R): The distance between the Pole and the Centre of Curvature.
- Principal Axis: The straight line passing through the Pole and the Centre of Curvature.
- Principal Focus (F): The point on the principal axis where rays parallel to the principal axis either converge (concave mirror) or appear to diverge from (convex mirror) after reflection.
- Focal Length (f): The distance between the Pole and the Principal Focus. It is half the Radius of Curvature (f = R/2).
4. Why is a convex mirror preferred as a rear-view mirror in vehicles?
A convex mirror is preferred as a rear-view mirror for two main reasons. Firstly, it always forms an erect and diminished image of the objects behind the vehicle, making it easy for the driver to interpret the scene. Secondly, it has a wider field of view than a plane or concave mirror of the same size. This allows the driver to see a much larger area of traffic behind them, significantly improving safety by reducing blind spots.
5. Under what conditions does a concave mirror form a virtual, erect, and magnified image?
A concave mirror, which typically forms real and inverted images, produces a virtual, erect, and magnified image under one specific condition: when the object is placed between the mirror's Pole (P) and its Principal Focus (F). This is the principle behind its use as a shaving mirror or a dentist's mirror, where a magnified view of a close object is required.
6. How does the New Cartesian Sign Convention help in solving problems related to spherical mirrors?
The New Cartesian Sign Convention provides a consistent set of rules for assigning positive or negative values to distances (object distance u, image distance v, focal length f) and heights. It helps in applying the mirror formula (1/v + 1/u = 1/f) and the magnification formula (m = -v/u) universally for both concave and convex mirrors without confusion. By defining the pole as the origin and the principal axis as the x-axis, it standardises calculations, allowing the results (like the position and nature of the image) to be interpreted correctly based on their sign.
7. What are some real-world examples that illustrate the uses of concave and convex mirrors?
Spherical mirrors have many practical applications based on their unique properties:
- Concave Mirror Examples: They are used in car headlights and searchlights to produce a powerful, parallel beam of light when the bulb is placed at the focus. They are also used as shaving mirrors and by dentists to get a magnified, erect image of the face or teeth.
- Convex Mirror Examples: Their most common use is as rear-view or side-view mirrors in vehicles to provide a wide field of view. They are also used for security purposes in shops and at sharp corners on roads to monitor a large area.

















