Differences between DVDs and CDs

[blazingcheese]

Does anyone here know the physical differences between DVDs and CDs/CD-ROMs? I don't care about the data capacity difference or other technical stuff like that, I want differences in the physical make up of the two discs.

For example, give me the differences in weight, thickness, etc. Those aren't the only things I want to know. Just list as many differences you know that are along that line.

As you may know from previous posts, I've been having an ongoing problem getting DVDs to play in my DVD-ROM drive, while CDs and CD-ROMs play fine. It's definately a hardware problem, I just need to know what's wrong, and I thought this information could help me. TIA

[Ryo94]

Some physics differences that I know between drives and discs.

Drives:
*Wave longitude of the laser: CD (780nm) DVD (635-650nm)
*Numeric opening of the laser: CD (0.45) DVD (0.60)

Discs:
*Thickness: CD (1.2mm -1 layer-) DVD (1.2mm -2x0.60 layers-)
*Track pitch (distance between tracks): CD (1.6 µm) DVD (0.74 µm)
*Longitude of the shortest pit: CD (0.83 µm) DVD (0.4 µm)
*A dvd has almost a density of 35000 TPI (tracks per inch) while the CD has less than the half.

Greetings.