DPS backlighting assignment.
I decided to improvise as my daughter threw away my backlighting model - Okay, it was only a dead fly but I had a plan and where do you find one of those at midnight!!! LOL!
The scene is lit by a 100w spot light directed through the prism and a 150w uplighter. Using a high ISO introduced the grainy effect on the refracted rainbow of light, which was a pleasing accident!