# Lens problem! Please check my work.

## Homework Statement

An object is placed 12.8 cm to the left of a diverging lens of focal length -6.35 cm. A converging lens of focal length 12.8 cm is placed a distance of d to the right of the diverging lens. Find the distance d that places the final image at infinity

1/f=1/di+1/do

## The Attempt at a Solution

I understand that I have a few unknowns and need to solve this a couple of times to discover the di:

So [/B]1/f=1/di +1/do : MAIN EQUATION
Di: 1/(-6.635)=1/di+1/(12.8cm). gives me di of -4.244 cm
Do2: 4.244+25.6=29.844 cm
1/do2+1/di2=1/f2 (1/2984)+1/di2=1/12.8cm

Eventually I end up with -22.41 cm.

I don't know if I am supposed to solve this for 2nd time through lens. Therefore, I thought I ended up -22.41 cm. However, that is not right. Please help.

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## Homework Statement

An object is placed 12.8 cm to the left of a diverging lens of focal length -6.35 cm. A converging lens of focal length 12.8 cm is placed a distance of d to the right of the diverging lens. Find the distance d that places the final image at infinity

1/f=1/di+1/do

## The Attempt at a Solution

I understand that I have a few unknowns and need to solve this a couple of times to discover the di:

So [/B]1/f=1/di +1/do : MAIN EQUATION
Di: 1/(-6.635)=1/di+1/(12.8cm). gives me di of -4.244 cm
Do2: 4.244+25.6=29.844 cm
1/do2+1/di2=1/f2 (1/2984)+1/di2=1/12.8cm

Eventually I end up with -22.41 cm.

I don't know if I am supposed to solve this for 2nd time through lens. Therefore, I thought I ended up -22.41 cm. However, that is not right. Please help.