Optically Worked Double Convex Glass Lens, 75mm Diameter, 300mm Focal Length, Alternate Model Capacity_125mL this low-current 2mA buzzer on

this low-current 2mA buzzer on a demonstration base sounds whenever current flows through the closed circuit

retaining field strength across years of classroom handling

sized for student-bench stability during routine glassware assembly

the cylindrical concave curvature spreading light along a single axis for line-focus and divergence demos

and brass strips radiating to the rim

Optically Worked Double Convex Glass Lens, 75mm Diameter, 300mm Focal Length, Alternate Model Capacity_125mL this low-current 2mA buzzer onAlternate model 75mm double convex glass lens at 300mm focal length, the optically worked surfaces and ground polished edges parallel to the main line 300mm focal lens for backup stock use.