(a) An object is placed at the centre of curvature (c ) of a concave mirror. Draw the ray diagram to depict the position, size and nature of image formed.
(b) Find the focal length of a lens of power - 2.0 D. What type of lens is this ?

Explanation

### Step-by-Step Solution

#### Part (a): Ray Diagram for a Concave Mirror

1. **Identify the Components**:
- Draw a concave mirror with its principal axis. Mark the center of curvature (C) and the focal point (F), which is halfway between the mirror's surface and C.

2. **Position the Object**:
...