Ulexite: Fiber Optic Rock - Physics Demonstrations - Ulexite: Fiber Optic Rock | Physics Undergraduate Labs

If using a laser pointer for the advanced demonstration, ensure it is Class 2 or lower (<1 mW). Never point the laser at students or allow direct eye exposure. Brief the class on laser safety before beginning this portion of the demonstration.

Purpose

A naturally occurring "fiber optic rock" transmits images from its base to its top surface via total internal reflection in parallel crystal fibers. Comparing ulexite to a plain acrylic block highlights the difference between fiber optic image transmission (requires contact) and simple refraction (works at a distance).

Small translucent ulexite specimen (~1x1x2 cm) resting on a large white letter A on a red background, with part of the letter's edge visible through the top of the stone

Translucent ulexite stone on printed text reading 'A Rock Called Ulexite' with word 'Rock' visible through the crystal

Figure 1: Ulexite on a printed letter. The boundary between the white letter and red background is transmitted through the stone to its top surface.

Figure 2: The word 'Rock' appears on the top surface of the ulexite when the stone is in direct contact with the paper, showing fiber optic image transmission from base to top.

Safety Warnings

Warning: Laser Safety

Purpose