CD Diffraction and quick fun bits for teaching light

Well, the FOCUS Workshop/DMAPT Meeting was Awesome!!! I learned lots, and have probably already forgotten some great stuff.

I presented CD Diffraction and there was a question about how to remove the label from the back of a CD. I’ve never been good at this, and said as much. Some people just have the knack while most don’t. One of the audience members came to my rescue. He is one of the editors of ArborScientific’s Cool Stuff Newsletter (which is great btw). In Newsletter 22 they covered CD Diffraction and the used packing tape to remove the label.

Apparently you can just wrap the tape, sticky side out, around you hand and then just press down on the label and the tape will peel it off. Brilliant!!! The added bonus is you aren’t left with little foil bits scattered around the classroom.

More Diffraction
Find the diameter of a hair.

  1. Point a laser pointer at a hair. You will see a diffraction pattern on the wall.
  2. How do you line it all up? Tape the hair to the laser so that it is draped over the front.
  3. Measure the distance to the screen and the distance from the laser spot to the bands.
  4. Plug the numbers into the same formula from the CD Spacing activity from my last post.

Model DNA X-Ray Diffraction.

  • Same instructions as above, but use a 2-ply thread instead of a hair.
  • The 2-ply thread is a double helix
  • Shine on a screen or piece of paper
  • You should see a pattern similar to the X-Ray Diffraction picture that led to the discovery of DNA’s structure.
  • The picture to the right is Rosalind Franklin’s picture that was used by Watson and Crick.

I’ll try to post more stuff from the Workshop over the next few days.