Question

The focal length of a concave lens is 20 cm. If an object is placed at a distance of 50 cm in front of this concave lens, where is the image formed? What is the nature of the image?

Answer 1

Focal length of concave lens = 20 cm

Object distance = 50 cm

Using lens formula, $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$$\begin{gathered} \Rightarrow \frac{1}{v}=\frac{1}{-20}+\frac{1}{-50}=-\frac{7}{100} \\ \Rightarrow v=-\frac{100}{7}\mathrm{cm} \end{gathered}$$

The image formed is virtual, erect and diminished in size.