### CD/DVD pit depth

is given by $$d = \frac{\lambda}{4}$$where $$\lambda$$ is the wavelength of the laser for the CD/DVD reader.The distance corresponds to a total additional distance of $$\frac{\lambda}{2}$$ travelled by the laser light at a pit-land interface (corresponding to binary 1).

DVDs (shorter pit length and double layers) have about 7 times the storage capacity of CDs. Changing or reducing the laser wavelength can increase the resolution, by decreasing $$\theta= 1.22 \frac{\lambda}{b}$$, thus allowing more pits and therefore greater storage capacity. Bluray technology uses shorter wavelength laser light.