1. Optical Media
Key Revision Points

2. Optical Media In size order:
CD – 700MB
DVD – 4.7GB
Blu-Ray – 25GB
Variations: Each of the above can come in 3 formats:
ROM e.g. BD-ROM Read Only
R e.g. DVD-R Can be written to once
RW e.g. DVD-RW Rewritable (can write to many times)

3. Operation All optical media work on the same principle
Learn these steps!
Data on the CD/DVD/Blu Ray stored as microscopic indentations called pits
Disk spins
Arm/rail containing a laser moves in and out over the spinning disk
A laser beam is shone onto the disk where it hits a pit or land(flat area)
The reflected beam translated into binary

4. Benefits/Drawbacks Benefits Drawbacks
Relatively Cheap (per GB of data)
Low capacity compared with modern USB flash drives
Portable
Increasing Internet speeds have made cloud storage an alternative for backing up personal data
Water/shock proof
Easily scratched

5. Textbook and Firefly
Textbook page 7