Hartley's Rotatable Optical Disc Material_Muslin a step up from the

a step up from the 70mm model with extended pole separation that gives field-mapping experiments more room along the magnet axis

this analog DC microammeter measures 0-100uA at 2uA resolution on a tabletop housing

and troubleshooting exercises

with a (Br) marking visible on one face for easy identification

and 26 SWG - sized as the matched replacement set for the PH0730 sonometer

Hartley's Rotatable Optical Disc Material_Muslin a step up from the230mm disc graduated 0 360 degrees in 1 degree steps locks in any position alongside a rotatable lamp house and six magnetic acrylic elements for full ray tracing studies of reflection and refraction.