Question

An object placed 84 cm in front of a converging lens forms an image 24 cm behind the lens. What is the focal length of the lens?

Answer 1

`\begin{equation*} 18.67\text{ cm} \end{equation*}`

Step-by-step explanation

Parameters given:

Object distance, u = -84 cm

Image distance, v = 24 cm

To find the focal length, apply the formula for focal length for a converging lens:

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

Therefore, the focal length of the lens is:

`\begin{gathered} (1)/(f)=(1)/(24)-(1)/(-84)=(1)/(24)+(1)/(84) \\ \\ (1)/(f)=(7+2)/(168)=(9)/(168) \\ \\ f=(168)/(9) \\ \\ f=18.67\text{ cm} \end{gathered}`

That is the answer.