Optically Worked Double Concave Glass Lens, 75mm Diameter, 200mm Focal Length

This double concave (biconcave) lens is made from optically worked glass with a highly polished surface and ground edges. It measures 75mm (3 inches) in diameter with a diverging focal length of 200mm and a refractive index of 1.52. As a diverging lens, it causes parallel light rays to spread apart after passing through, producing virtual images. This makes it suitable for classroom demonstrations in optics covering topics such as focal length, image formation, ray diagrams, and the behavior of diverging lenses.