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 1.5in diameter, 0.2 weight
Refill TapWater Tour, Classroom investigation of how and why the characteristics of tap water can vary and affect everyday activities, Background information, test materials included for pH, chlorine, hardness, copper, iron, With Instructor, Student Manuals