CD and DVD lines per inch

I am trying to find out how many lines per inch or mm or cm are written to a CD and a DVD disc. This is for a science project for some students to explain how these discs can be used to project a spectrum. A google search turned up little info of use. Anybody know where I can find this info or the info itself ?

Thanks

 

Yes it is - it gives the spaacing between lines, which is what we need to figure out the various problems. Thanks for the site.