Question

What is the focal length of a lens if an object placed 3.28 cm from the lens produces an image that is 4.11 cm in front of the lens?

Answer 1

1.82 cm

Step-by-step explanation:

The relationship between the object distance (p), image distance (q) and focal length (f) is given by
`(1)/(p)+(1)/(q)=(1)/(f)`

According to question,

Object distance (p) = 3.28 cm

Image distance (q) = 4.11 cm

Therefore,

`(1)/(3.28)+(1)/(4.11)=(1)/(f)\\(3.28+4.11)/(3.28* 4.11)=(1)/(f)\\f=(3.28* 4.11)/(3.28+4.11)\\=(13.48)/(7.39)\\=1.82\,\,cm`