Science Buddies: "Ask an Expert"

I am working on the "Using a Laser Pointer to Measure Data Track Spacing on CD's and DVD's" project (https://www.sciencebuddies.org/science- ... p011.shtml), and am calculating the spacing from my measurements. I have entered the measurements in a Microsoft Works Spreadsheet (Excel), and am wondering if there is an easier way to calculate the values in the sheet than doing them all by hand. Any help would be very appreciated.

Also, I have reviewed the boards and found another person on this project had very different results. I am concerned that my measurements may be off, and therefore I would like to know an average range, and also if the disks used would affect the project drastically. One of my hand calculations was 588.2 on a CD-ROM with 566Mb of data. Is this acceptable? Also, I am curious to know if the ROM factor in a CD-ROM would affect the readings. Thanks.

In response to your first question, yes, you can use Excel to do the calculations for you. Excel formulas are fairly easy once you understand how they work.

Here is a fairly simple tutorial describing Excel formulas: http://spreadsheets.about.com/od/excelf ... _begin.htm

Excel has all the various calculations you might need, for example, SIN(theta), etc. Pay attention to the suggestion about radians in the description of the experiment.

Let us know if you have any more questions about Excel.

In terms of your results, I'm not sure exactly what you're asking. Is that number you calculated supposed to be the spiral separation (pitch) in nanometers? If so, yes that seems quite a bit too small unless you're actually looking at a DVD rather than a CD. CD pitches tend to be around 1.5um - 1.7um. DVDs typically run about .74um pitch.