Question

An object is placed at a distance of 20cm from the pole of a concave mirror of a focal length of 10cm. The distance of the image formed is?

Answer 1

Step 1: Given

the object distance, $u=-20cm$

the focal length of the mirror, $f=10cm$

Step 2: Finding the image distance using the mirror formula:

We know that

$$\begin{gathered} \frac{1}{u}+\frac{1}{v}=\frac{1}{f} \\ \Rightarrow \frac{1}{v}=\frac{1}{f}-\frac{1}{u} \\ Bysubstitutingthegivenvalues,weget \\ \frac{1}{v}=\frac{1}{-10}-\frac{1}{-20} \\ =\frac{-1}{10}+\frac{1}{20} \\ =\frac{-2+1}{20} \\ =\frac{-1}{20} \\ Therefore,v=-20cm \end{gathered}$$

The distance of the image formed is -20cm and the nature of the image is ‘Virtual’.