Find the object location with ray optics

[Workout]

Homework Statement

A 1.0-cm-tall object is placed 4.0cm from a diverging lens of focal length 6.0cm. Using both ray tracing and the thin lens formula, find the location and orientation of the image.

Homework Equations

-1/f = 1/so + 1/si
m = -si/so = hi/ho

The Attempt at a Solution

-1/6cm = 1/4cm + 1/si
si = -2.40 cm

Okay so attached my ray tracing diagram.. (sorry for the crappy camera quality), but the point where the Si crosses the ho is supposed to be where the object distance is.. and i measured with my ruler that it is 0.4cm, not 2.4cm. What am I doing wrong in the drawing?

 

[TSny]

You haven't correctly drawn the ray that travels horizontally toward the lens. Hint: for this ray you'll need to use one of the focal points.

 

[Basic_Physics]

Rays traveling parallel to the principal axis are refracted through the focal point of the lens.