A body of length 6 cm is placed 10cm from a concave mirror of focal length 20cm. Find the position, size, and nature of the image.

Explanation

Consider the situation shown in the figure below which also includes the coordinate system.
Here, ` u=-10cm`
`f=-20cm`
Subtituting in the equation,
`(1)/(v)+(1)/(u)=(1)/(f)` , we get
`v=+20 cm`
Thus, the image is formed 20 cm behind the mirror, magnification `+2` , erect and virtual.