How does optical storage like CDs and DVDs work?

Optical storage like CDs and DVDs work by using lasers to read and write data on their reflective surfaces.

Optical storage devices such as CDs (Compact Discs) and DVDs (Digital Versatile Discs) utilise a technology that involves the use of light, specifically lasers, to store and retrieve data. The fundamental principle behind this technology is the interaction between the laser light and the disc's surface, which is typically coated with a reflective material.

The process begins with the writing or burning of data onto the disc. This is achieved by a high-powered laser that creates tiny indentations, known as pits, on the disc's surface. These pits are arranged in a spiral track that starts from the centre of the disc and moves outward. The areas between the pits are known as lands. The pattern of pits and lands represents the binary data (0s and 1s) that computers understand.

When it comes to reading the data, a lower-powered laser is used. This laser beam is directed onto the disc's surface and as it moves along the spiral track, it is reflected back differently by the pits and lands. The pits, due to their indentation, scatter the laser light, while the lands, being flat, reflect the light straight back. This difference in reflection is detected by a photodiode sensor and is translated into binary data.

The main advantage of optical storage devices is their durability and longevity. Unlike magnetic storage devices, they are not susceptible to data loss from exposure to magnetic fields or mechanical failure. However, they do have their limitations. The amount of data that can be stored is finite and determined by the physical size of the disc and the precision of the laser. Furthermore, the speed at which data can be read or written is generally slower than other storage technologies.

In summary, optical storage devices like CDs and DVDs work by using lasers to create and read a pattern of pits and lands on a reflective surface, representing binary data. This technology offers a reliable and durable means of data storage, albeit with certain limitations.