6D20.XX Diffraction Through Money
Modern Canadian plastic money has a diffractive element in it as a security feature. When a laser beam shines through the maple leaf on the bill, it produces a diffracted image telling you what the value of the bill is. Another way to see this is by looking at a point source of light through the maple leaf; this works with the naked eye.
-  Canadian plastic bill
-  Red laser pointer
-  Green laser pointer
-  Desk lamp
- Plug in the desk lamp.
- Lasers can cause blindness. Use with caution.
- This demo is untested in a large class.
- Turn off the lights.
- Shine a laser pointer through the maple leaf grating onto a prominent wall.
- Turn on the desk lamp and point it at the class for students to try on their own money.
- Turn off the lamp and turn on the lights.
- PIRA 6D20.XX
- CCL Industries makes the substrate on which Canada's plastic bills are printed. They have an advertising-ish promotional journal called Specimen with some details about the money:
Specimen, Issue 1 (December 2012)
They call their diffraction grating technology "Eclipse."
- Don't attempt this at home!
- Red lasers seem to give a more legible pattern. The pattern may be bigger, and red light is likely less sensitive to imperfections in the grating.
- The grating is probably a phase grating.
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.