Upper surface roughness of a 250 GB platters
It scans a 250 GB Platter with the Laser scanner the following picture emerges.
The "Roughness" or amplitude is in the range -0 1µm. However, after dust has Definition a particle size of 2.5 10 µm, 25-100 is therefore greater. This is among other things a reason why (funktioniernde) hard drives should not be opened.