[Physics Class Notes] on Spherical Mirrors Pdf for Exam

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:

• 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.