Sketchbook work for Michaels class, sphere and some cube drawings, its all about those shadows! 😉
‘The Dimensions of colour’ webpage by David Briggs has some great articles; I found this whilst researching into lighting spheres. Theres also other great articles found on his page.
http://www.huevaluechroma.com/021.php
Briggs has included some useful interactive spheres where you can change the direction of light. Handy tool when studying light and shadow. (Link above)
(Image above; Copyright. David Briggs)