Question

A converging lens has focal length of 12 cm. Calculate at what distance the object should be placed from the lens so that it forms an image at 48 cm on the other side of the lens.

Answer 1

 

Given,

Image distance: v = +48 cm         (It is on the other side of the lens)

Focal length: f = +12 cm               (It is a converging lens or convex lens)

Object distance: u =?                    (To be calculated)

Now, putting these values in the lens formula:-

`1/f=1/v-1/u`

`rArr1/12=1/48-1/u`

`rArr1/u=1/48-1/12`

`rArr1/u=(1-4)/48`

`rArr1/u=(-1)/16`

`rArru=-16" cm"`

Therefore, the object should be placed at a distance of 16 cm from the convex lens. The minus sign with the object distance shows that the object is on its left side.