What does a CD look like?
A compact disc is a thin, circular disc of metal and plastic about 12cm (just over 4.5 inches) in diameter. 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.
What are pits on a CD?
An indentation in an optical medium such as a CD-ROM or DVD. The laser beam is either absorbed in the pit or reflects off the non-indented areas, which are called “lands.” Using various algorithms, the reflections are converted into 0 and 1 bits.
What are pits and lands in CD?
CD data are stored as a series of tiny indentations known as “pits”, encoded in a spiral track molded into the top of the polycarbonate layer. The areas between pits are known as “lands”.
What does the surface of a DVD look like?
A DVD is composed of several layers of plastic, totaling about 1.2 millimeters thick. Each layer is created by injection molding polycarbonate plastic. You will often read about “pits” on a DVD instead of bumps. They appear as pits on the aluminum side, but on the side that the laser reads from, they are bumps.
What is CD in chemistry?
cadmium
cadmium (Cd), chemical element, a metal of Group 12 (IIb, or zinc group) of the periodic table.
Is a DVD a CD?
A Digital Versatile Disc or Digital Video Disc (DVD) is similar to a CD-ROM in that you can only read data from it. The main difference is that the DVD can store much more data than a CD-ROM, CD-R, or CD-RW. DVD+R is a recordable DVD format similar to CD-R. The disc cannot be recorded onto a second time.
How do CD’s work?
When a depositor purchases a certificate of deposit, they agree to leave a certain amount of money on deposit at the bank for a certain period of time, such as one year. In exchange, the bank agrees to pay them a predetermined interest rate and guarantees the repayment of their principal at the end of the term.
What is the difference between a pit and a land?
As nouns the difference between pit and land is that pit is a hole in the ground or pit can be a seed inside a fruit; a stone or pip inside a fruit while land is the part of earth which is not covered by oceans or other bodies of water.
How does a laser read a CD?
The surface of the CD contains one long spiral track of data. 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.
How are CDs made?
CDs consist of three layers of materials: A base layer made of a polycarbonate plastic. A thin layer of aluminum coating over the polycarbonate plastic. A clear protective acrylic coating over the aluminum layer.
Is Cd a metal?
Cadmium (Cd) is a soft, malleable, bluish white metal found in zinc ores, and to a much lesser extent, in the cadmium mineral greenockite. Cadmium became an important metal in the production of nickel-cadmium (Ni-Cd) rechargeable batteries and as a sacrificial corrosion-protection coating for iron and steel.
What are the properties of Cd?
Table 4-2Physical and Chemical Properties of Cadmium and Compounds a
| Property | Cadmium | Cadmium carbonate |
|---|---|---|
| Melting point | 568 °Cb | Decomposes at 950 °C |
| Boiling point | 960 °Cb | Decomposes at 950 °C |
| Density at 20 °C | 4.047g/cm3 at 25 °Ce | Crystals 8.15 g/cm3; amorphous powder 6.95 g/cm3c |
| Odor | Odorlessc | Odorless |