Physics
Optics Caliper
A light weight caliper designed to allow measurements in the dark during optical experiments.
This lightweight plastic caliper is perfect for measuring images in the dark. Simply span the object and then use a scale to measure the distance. For approximate measurements, use the built-in cm scale on the calipers.
https://www.pasco.com/products/lab-apparatus/light-and-optics/diffraction/os-8468#specs-panel