T - geometric optics
PX284 - T1 - wavefronts and rays
PX284 - T2 - fermat's principle
PX284 - T3a - imaging
PX284 - T3b - spherical surface using intersecting cords theorem
PX284 - T3c - spherical surface using trigonometric properties
PX284 - T4 - thin lens
PX284 - T5 - principal rays
PX284 - T6 - images
PX284 - T7 - telescopes