I made a lens in Freecad which I imported into Blender. Being new to Blender I managed to;
a) position a red bulb behind the object b) give the object a material, set transparency, raytrace and a refractive index.
At this point I could see the red light from the front but not through most of the object, while the camera at the rear. I then went about positioning the camera behind the object and inserting a plane onto which I was hoping to show the refracted light. It appears to ignore the lens.
Files and screenshot here:
Can anyone advise what steps are required to make it work?