Overview for Blu-ray Discs

The name Blu-ray Disc is derived from the blue-violet
laser used to read and write this type of disc. Because
of its shorter wavelengh (405nm), substantially more
data can be stored on one of these than on the DVD
format. The DVD format uses a red (650 nm) laser. A
single layer Blu-ray Disc can store 25 gigabytes (GB),
over five times the size of a single layer DVD (4.7 GB).
Did you know a dual layer Blu-ray Disc can store 50 GB?
That is almost six times the size
of a dual layer DVD (8.5 GB).



Hard coating technology

The recent introduction of a clear polymer coating has
given Blu-ray Discs substantial scratch resistance.


Blu-ray Disc is currently in a format war with the rival
format HD DVD (more on that soon).

source: www.wikipedia.com