Spherical Mirrors – Sign Conventions

Table of Contents

• Mirror Equation
• Cartesian Sign Conventions for a Spherical Mirror
• Summary
• What’s Next?

In the previous segment, we learnt about the Mirror equation and its derivation. In this segment, let us understand the sign conventions for a spherical mirror.

What is the Mirror equation?

• Consider an object in front of a spherical mirror whose ray diagram is shown below.

Figure 1

Here, the centre of curvature, the principal focus, and the pole are represented by the points ?, ?, and ? respectively.

• The mirror equation is ¹

?

= 1 +

?

¹ which provides a relation between the distance of the

?

object from the mirror (?), the distance of its image from the mirror (?), and the distance between the principal focus and the pole (?).

• All the distances of the mirror equation are taken from the pole of the mirror.
• The mirror equation is true for all types of spherical mirrors.
• The mirror equation is independent of the position of the object.