What is the medium used in optical storage systems for reading and recording data ?

Optical storage systems, such as Compact Discs (CDs), Digital Versatile Discs (DVDs), and Blu-ray discs, use laser light as the primary medium for reading and recording data. The term "optical" refers to the use of light to retrieve or store information on a physical medium.

• Recording: A high-intensity laser beam is used to create microscopic patterns (pits and lands) on the reflective surface of the disc.
• Reading: A lower-intensity laser beam is reflected off these patterns. A photodiode sensor detects the changes in the intensity of the reflected light, which the system then translates into binary data (0s and 1s).

Different types of optical storage use different laser wavelengths: CDs use infrared lasers (780 nm), DVDs use red lasers (650 nm), and Blu-ray discs use blue-violet lasers (405 nm).