Question

Where would you need to place an object to make its image appear 17.22 cm away from a lens if the lens has a focal length of 3.05 cm?

Answer 1

Given,

The image distance, v=17.22 cm

The focal length of the lens, f=3.05 cm

From the thin lens formula,

`\begin{gathered} (1)/(f)=(1)/(u)+(1)/(v) \\ \end{gathered}`

Where u is the object distance.

On rearranging the above equation,

`\begin{gathered} (1)/(u)=(1)/(f)-(1)/(v) \\ =(v-f)/(vf) \\ \Rightarrow u=(vf)/(v-f) \end{gathered}`

On substituting the known values,

`\begin{gathered} u=(17.22*3.05)/(17.22-3.05) \\ =3.71\text{ cm} \end{gathered}`

Thus the object distance should be 3.71 cm