# Homework Help: Converging lenses

1. Jul 21, 2013

### aChordate

1. The problem statement, all variables and given/known data

An object is in front of a converging lens with a focal length of 11.0 cm. The lens
produces a real image located 25.0 cm from the lens. If the lens is replaced by a new lens
(in the same position) that has a focal length of 32.0 cm, what is the image distance of the
new lens? Is the image real or virtual?

2. Relevant equations

Thin lens equation
1/f=1/d0+1/di

3. The attempt at a solution

lens 1:

1/+11*10-2=1/dO+1/+25.0*10-2

dO=0.196m

lens2:

1/+32.0*10-2=1/0.196m+1/di

di=-0.506m

Virtual image

2. Jul 21, 2013

### collinsmark

Your approach is correct.

Your answer is pretty close, but there are some rounding errors. You might want to try again, but keep more significant figures in the intermediate steps.

3. Jul 22, 2013

### aChordate

I got -.509 on the second try. Hopefully that is correct.

4. Jul 22, 2013

### collinsmark

Yup. (Don't forget your units though.)