Reflection of Light by Spherical Mirrors

By Aditya Priyant|Updated : August 9th, 2017

A. Reflection

The Laws of Reflection are: 

  1. The angle of incidence equals the angle of reflection: i=r
  2. The incident ray, the normal to the mirror and the reflected ray lie in the same plane.

Fermat’s Principle

In going from one point to another, a light ray takes the path that requires the minimum time.

Real / Virtual Object (Image):

When a group of incident rays strike a surface, the point from which they diverge (light energy actually present, real) or the point at which they try to converge (appear to be coming from, virtual) is known as object.

After reflection we get a group of reflected rays.

The point of convergence of reflected rays (actually passes, real) or the point from which they appear to diverge (seem to pass, virtual) is known as the image of the object.

A real image will appear on a screen at its position while a virtual image will not.

Sign Convention:

  1. All distances are measured from the pole (as origin). Distance of the object is called the object distance (u) and that of the image is called image distance (v).
  2. All real distances are taken positive while that of virtual points will be taken negative.

Lenses and Mirrors


byjusexamprepC: centre of curvature angle AOB: aperture O: pole of mirror OC = AC = BC = R = radius of curvature


The point where the rays parallel (and close) to the principal axis on reflection from a concave mirror converge (real point) after reflection, or in case of a convex mirror rays seem to diverge away (virtual point) from focus after reflection. The distance of focus from pole is called as focal length (f).


Mirror Equation, Magnification:

Object distance, image distance and focal length in mirrors are related by the equation:


The ratio of the image size (I) to the object size (o) is called magnification (M) which equals ratio of image to object distance.


Ray Diagrams:

Basic laws followed by reflection of light rays from mirrors.

A light ray parallel to principal axis passes through focus or seem to diverge from it (for convex) after reflection.


A light ray passing through focus or appear to diverge at it (for convex) becomes parallel to principal axis after reflection.


A light ray striking the mirror normally will he reflected along the same path.

Image Formation for a Real Linear Object:

Image formation by a concave mirror













Convex Mirror:


Object position: anywhere in front of mirror

Image position and features: behind the mirror, between pole and F, virtual, erect & diminished.

Observe as object nears the pole, image also comes closer to the pole.

Some Important Results:

If a light ray is turned back (strikes a reflecting surface normally), it will retrace its path called reversibility. This is followed for all mirrors and lenses.

For plane mirrors, focal length can be taken as infinite.

When a light ray is reflected, its angle of deviation = 180° - 2i

If two plane mirrors are inclined at an angle θ with each other, total number of images observed is equal to the smallest integer greater than or equal to image021


Comment below with your queries on Reflection. Also, share it with your friends. Check out short notes on rest of the topics of Ray Optics below:





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MohitOct 12, 2016

Product of refractive index and sine of angle of refraction is constant
Harsh Singh

Harsh SinghOct 12, 2016

Sir pls provide notes of alternating currents ........ That will be a great help for me
Ayush Rawat

Ayush RawatOct 17, 2016

I could'nt find the material for refraction through lens and lens maker formula and that material ,  can you please help me
Vedant Vyavahare
Sir If I start study from now then I can crack jee main ?????

RahulMay 13, 2017

Thanks a lot sir for this notes
Nikhil Tomar Sirsali V
Sir thanks for the notes.
Please add more images to the notes.
Vishal Dhas

Vishal DhasDec 25, 2017

I want short notes on Elasticity
Manish Sharma
Sir i want notes on electrochemistry

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