6A02.35 Laser and Chalk Dust
Straight-line propagation of light
Chalk dust is spread in the path of a laser beam. The dust causes light scattering in the beam path, rendering it visible. Note: this demonstration is appropriate for large lecture halls.
-  He-Ne Laser
-  Lab stand
-  90-degree clamp
-  Chalk
-  Chalkboard brushes
-  Mirror
- Mount the laser on the lab stand, with the laser pointing to the side or far over the heads of students.
- Plug in the laser.
- Fill the brushes with chalk dust.
- Lasers can cause blindness. Use with caution.
- Turn off the lights.
- Turn on the laser.
- Clap the brushes together along the laser beam's path. Holding the brushes just underneath the beam works well.
- [Optional] Hold a mirror in the beam path to show reflection of the laser beam.
- Turn off the laser.
- Turn on the lights.
- PIRA 6A02.35
- Don't attempt this at home!
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.