# Reflection of Light Part-2

** ****Use of Concave Mirror:**

** ****Use of Convex Mirror:**

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**Sign Convention for Reflection by Spherical Mirrors**

**The conventions are as follows –**

**(i) **The object is always placed to the left of the mirror. This implies that the light from the object falls on the mirror from the left-hand side.

**(ii)** All distances parallel to the principal axis are measured from the pole of the mirror.

**(iii)** All the distances measured to the right of the origin (along + x-axis) are taken as positive while those measured to the left of the origin (along – x-axis) are taken as negative.

**(iv)** Distances measured perpendicular to and above the principal axis (along + y-axis) are taken as positive.

**(v)** Distances measured perpendicular to and below the principal axis (along –y-axis) are taken as negative.

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**Mirror Formula and Magnification:**

## Mirror Formula

Now, that all these conventions are clear; let us know move on the mirror formula. Mirror Formula helps us to find:

- Image distance which is represented as ‘v’.
- Object distance which is represented as ‘u’.
- Focal length which is represented as ‘f’.

And is written as:

**Magnification**

It is represented as the ratio of the height of the image to the ratio of the height of the object. Magnification is denoted as the letter ‘m’. Where,

**Magnification (m) = h/h’**

h’ is the image height

h is the object height

Magnification can also be related to the image distance and object distance; therefore it can also be written as:

m = -v/u

Where v is the image distance and u is the object distance.

Hence, the expression for magnification (m) becomes:

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