An object is placed $20 \mathrm{cm}$ in front of a concave mirror of focal length $12 \mathrm{cm}$. Find the nature and position of the image formed in each case. 

An object is placed just outside the principal focus of concave mirror.

(a) Draw a ray diagram to show how the image is formed, and describe its size, position and nature.

(b) If the object is moved further away from the mirror, what changes are there in the position and size of the image?