Double Convex Lens, Highly polished, optically true lens is excellent for physics classroom demonstrations in optics and light refraction, with ground edges, great for physics classrooms, with highest grade, Size: 250 mm focal length, Lens measures 3in diameter, 0.2 weight
Inverting Spectacles, With Two Fully Rotating Inverting Prisms In A Shielded Spectacle Frame, The Inverting Prisms Produce A Lateral Inversion Of The Rays-The World Thus Turns Upside Down, This Also Enables A Better Understanding Of The Visual Perception Of Babies.