Double Convex Glass Lens, 50mm Diameter, 300-1000mm Focal Length Range Grade_Food Grade Push-button engagement on a hand-cranked

Push-button engagement on a hand-cranked single-sided cone clutch

Designed to measure Planck's constant through the photoelectric effect

Low temperature gradient- can withstand high temperatures & thermal shocks

holding a 20mm candle steady for thermal-expansion

Tensioner pulley keeps chain engagement consistent on this hand-cranked chain drive

Double Convex Glass Lens, 50mm Diameter, 300-1000mm Focal Length Range Grade_Food Grade Push-button engagement on a hand-crankedBuilt for long bench convergence flexibility, a 50mm double convex glass lens spanning 300 1000mm focal lengths gives projection style optics setups a single range rated element.