<https://lecdem.physics.umd.edu/tools-and-resources/forum-tr/l6/909-l6-22-optical-board-ray-diagram-virtual-image.html>
<http://schema.org/headline>
"L6-22: OPTICAL BOARD - RAY DIAGRAM - VIRTUAL IMAGE"
<https://lecdem.physics.umd.edu/tools-and-resources/forum-tr/l6/909-l6-22-optical-board-ray-diagram-virtual-image.html>