Question

A converging lens of focal length 20 cm is used to form a real image 1.0 m away from the lens. How far from the lens is the object?

Answer 1

0.25 m

Step-by-step explanation:

We can solve the problem by using the lens equation:

`(1)/(f)=(1)/(p)+(1)/(q)`

where

f is the focal length

p is the distance of the object from the lens

q is the distance of the image from the lens

In this problem, we have

f = +20 cm=+0.20 m (the focal length is positive for a converging lens)

q = +1.0 m (the image distance is positive for a real image)

Solving the equation for p, we find

`(1)/(p)=(1)/(f)-(1)/(q)=(1)/(0.20 m)-(1)/(1 m)=4 m^(-1)\\p=(1)/(4 m^(-1))=0.25 m`