What is the main difference between a CD and DVD?
The physical difference between a CD and DVD is the proximity of the tracks and the length of the pits. The pits on a CD are .5 microns wide and a minimum of .83 microns long. The tracks on a CD are 1.6 microns apart. A DVD is about half these dimensions. The track separations are only .74 microns and the pits are about .42 microns long. This is what enables a DVD to have a minimum of 6 times the amount of data.