Light – Reflection and Refraction — Part 1: Spherical mirrors and ray diagrams: visual lesson, CBSE Class 10 Science

Lesson

Light – Reflection and Refraction

Part 1 — how curved mirrors form images, and how to find those images with simple ray diagrams.

In this lesson you will

Define pole, centre of curvature, principal axis, principal focus and focal length, and relate R = 2f
Draw ray diagrams for a concave mirror for six object positions
Draw the ray diagram for a convex mirror and describe its image
State uses of concave and convex mirrors

Concept

Reflection: the two laws

Light falling on a polished surface is reflected. (1) The angle of incidence equals the angle of reflection. (2) The incident ray, the reflected ray and the normal at the point of incidence lie in the same plane. These laws hold for all reflecting surfaces, flat or curved.

Table of the properties of the image formed by a plane mirror
Plane mirror image	Property
Position	As far behind the mirror as the object is in front
Nature	Virtual and erect
Size	Same as the object
Orientation	Laterally inverted (left and right swapped)

Concept

Spherical mirrors: concave and convex

A spherical mirror is part of a hollow sphere. If the reflecting surface curves inwards (like the inside of a spoon), it is concave. If it bulges outwards (like the back of a spoon), it is convex.

Table comparing concave and convex mirrors by reflecting surface, effect on parallel rays and an everyday example
	Concave mirror	Convex mirror
Reflecting surface	Curves inwards, towards the object	Bulges outwards
Effect on parallel rays	Converges them	Diverges them
Everyday example	Inside of a steel spoon	Back of a steel spoon

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