Using a laser pointer to measure data track spacing on CDs.

[ryband0]

I am mentoring a 5th grade student and he selected this project from this sight. We are having a lot of trouble getting the different diffraction lines to show up. Does anyone have any tips on how to make it more precise? We have tried it with DVD's, CD's, and video games. At most we will get one or two lines, the picture shows like 5. Any ideas?

[ryband0]

I just tried again and was able to get 3 lines. One reflecting from the laser and angled ones off each side. I noticed when looking at the lasers in the reflection of the CD there was a 4th line, but theres no way to measure that even if I took a picture.

[deleted-73970]

Hi ryband0,

I understand your frustration, but as is the case with many projects, you might not get the same results that someone else did in the past. Luckily, you can work off of three lines for the calculations, as they should provide sufficient data. If you get more, certainly that would improve the calculations, but what you are currently seeing with your chosen incident angle is fine as it is.