"The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write to this type of disc. In part because of the shorter wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on a DVD, which uses a red (650 nm) laser. A dual-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a dual-layer DVD, or ten and a half times that of a single-layer DVD." Source: Wikipedia.
