What is the wavelength of DVD?
DVD uses light of 650 nm wavelength (red), as opposed to 780 nm (far-red, commonly called infrared) for CD.
Why does a Blu-ray Disc hold more data than a DVD?
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 wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red, 650 nm laser.
What is the wavelength of the light emitted by the laser used to read the data from a CD surface?
A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected.
What is the material used in CD and DVD so that the data can be stored?
It’s actually made of three layers. Most of a CD is made from a tough, brittle plastic called polycarbonate. Sandwiched in the middle there is a thin layer of aluminum. Finally, on top of the aluminum, is a protective layer of plastic and lacquer.
What is DVD short for?
‘ The original acronym came from ‘digital video disc. ‘ The DVD Forum decreed in 1999 that DVD, as an international standard, is simply three letters.
How do DVDs store data?
Digital versatile discs (DVDs) can store more information than compact discs (CDs) because they have smaller pits, placed closer together. It is the pattern of these pits burned onto a disc’s surface that encodes the 1’s and 0’s a player translates into sound and/or images.
How does a Blu-ray disc store data?
Unlike current DVDs, which use a red laser to read and write data, Blu-ray uses a blue laser. A blue laser has shorter wavelengths (405 nanometers) than a red laser (650 nanometers). The Blu-ray disc overcomes DVD-reading issues by placing the data on top of a 1.1 mm thick polycarbonate layer.
How much data can a Blu-ray hold?
Blu-ray Disc media include these features: 50GB capacity – Each disc can hold more than 10 standard DVDs. 25GB capacity – Each disc can hold more than 5 standard DVDs. Space for HD video recording – Massive hard disk backups and large multi-media files.
How does a laser read data on a compact disc?
The CD drive shines a laser at the surface of the CD and can detect the reflective areas and the bumps by the amount of laser light they reflect. The drive converts the reflections into 1s and 0s to read digital data from the disc.
Why is laser light so intense?
Laser light thus differs from ordinary sources of light like a candle or sunlight, by having all its radiation power centred around a particular wavelength (in the optical or infrared), i.e. in a narrow bandwidth. This is what gives the laser its intensity.
How does data store inside a DVD R?
Like CD-Rs, DVD recordable uses dye to store the data. During the burning of a single bit, the laser’s intensity affects the reflective properties of the burned dye. By varying the laser intensity quickly, high density data is written in precise tracks.
What is used to read the data of the data track of a CD?
What is the wavelength of DVD Laser?
DVD devices are based on Diode laser with red wavelength of 650 nm. As we saw, the exact wavelength is a critical parameter in reading the information, since the process is based on the interference between the beams reflected from different depths inside the recording media.
What is the wavelength of a red laser light?
Measure the L = Distance of laser beam above paper w = Distance between diffraction spots A red laser light has a wavelength of about λ = 650 nanometers (6.5 ×10-7 meters). Number of DVD Tracks CD Track Spacing
How much data is stored on a DVD?
The new devices can store information on both sides, so the total amount of information is 9.4 GB. The size of the DVD is the same as CD, but because it use a shorter wavelength, the pits can be smaller (minimum size 0.4 µm) and so is the distance between tracks (0.74 µm).
What is wavelength and why is it important in optical recording?
As we saw, the exact wavelength is a critical parameter in reading the information, since the process is based on the interference between the beams reflected from different depths inside the recording media. In order for the new DVD machines to be able to read CD-ROM media, two separate optical pickups need to be inside.