Under “Physics Education” menu, you can find a list of notes and handouts that I have made for my college-level students. These are materials which usually are not presented properly by textbooks or instructors. For instance, the sign convention for lenses and mirrors is a confusing topic for many students, especially in lesne systems. I believe bringing all these materials under one page in form of tables and picture, would resolve students confusion. I hope you find them helpful. Feel free to email me if you have suggestions or comments.