Let us understand the concept of image formation by a convex mirror through the following activity.
- Hold a convex mirror in one hand.
- On the other hand, hold a pencil in the upright position.
- Examine the pencil's reflection in the mirror.
- Is the image inverted or upright? Is it enlarged or diminished?
- Slowly move the pencil away from the mirror. Is the image shrinking or expanding?
- Carefully repeat this activity.
Will the image move closer to or farther away from the focus as the object is moved away from the mirror?
Pencil in front of a convex mirror - Sample
For the purpose of studying the image formed by a convex mirror, we consider two positions of the object. The first is when the object is infinitely far away from the mirror, and the second is when the object is finitely far away from the mirror. The below diagram shows, the ray diagrams for the formation of an image by a convex mirror for these two positions of the object.
Case 1: At infinity
Case 2: Between the infinity and the pole of the mirror
The below table shows the nature and position of the object formed by the convex mirror.