Question

A concave mirror has focal length 20cm,an object is placed at a distance of 16cm from it, find position of the image.<br />​

Answer 1

The Answer for your question with illustration..

Answer 2

Answer:

The position of the image is 80cm behind the concave mirror.

Explanation:

Given that for a concave mirror:

the focal length is given $f=-20cm$

The object placed, $u=-16cm$

By applying the mirror formula:

              $\frac{1}{f} =\frac{1}{v} +\frac{1}{u}$

           $\frac{1}{-20} =\frac{1}{v} +\frac{1}{-16}$

⇒             $\frac{1}{v} =\frac{1}{-20} +\frac{1}{16}$

⇒             $\frac{1}{v}=\frac{20-16}{(20)(-16)}$

⇒             $\frac{1}{v} =\frac{1}{80}$

∴             $v=+80cm$

Therefore the image is virtual as well as real and 80cm behind the concave mirror.