Question

An object of height $5$cm placed at a distance of $4$ cm from a convex lens of focal length $6$cm, locate the position of image.

Answer 1

Step 1-

Given data

The height of the object h1 = $5$ cm,

the distance of the object from the convex lens u = - $4$cm,

the focal length of the convex lens = $6$ cm,

let the distance of the image = v

Step 2-

Calculation of the position of the image

formula used - lens formula,

$$\begin{gathered} \frac{1}{f}=\frac{1}{v}-\frac{1}{u} \\ \frac{1}{6}=\frac{1}{v}-\frac{1}{-4} \\ \frac{1}{6}=\frac{1}{v}+\frac{1}{4} \\ \frac{1}{6}-\frac{1}{4}=\frac{1}{v} \\ \frac{4-6}{24}=\frac{1}{v} \\ v=-12cm \end{gathered}$$

Hence the image is obtained at $12$ cm behind the lens.