Calculating Focal Length of a Converging Lens Using Object and Image Distances

[whitehorsey]

Lens -- find the focal length

1. An object 3.0 cm tall is placed 20 cm in front of a converging lens. A real image is formed 10 cm from the lens. What is the focal length of the lens?



2. 1/f = 1/d_o + 1/d_i



3. 1/f = 1/d_o + 1/d_i
1/f = 1/20 + 1/10
f = 6.667 cm

I'm not sure if this is right and if you can can you show me how the diagram would look like. Thank You!

 

[Doc Al]

Your solution is correct. To learn about ray diagrams, see: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/raydiag.html#c1"

 

[Redbelly98]

Looks good.

For a diagram, look here:
https://www.physicsforums.com/library.php?do=view_item&itemid=148
Click the 1st image under "Images", on the right side of the page.

 

[whitehorsey]

Thank You!