cdbrännare?

hur skall jag tänka här?

A CD-burner works at the wavelength 850 nm and uses a focusing lens of
diameter 3.0 mm and focal width of 2.0 mm.
a) Is it possible to “see” distances on the CD disc of the order of 1 micron?
b) What is the longest wavelength one can use to be able to resolve 1.0 microns?