Coated Optics

Physics (Optics) Help Destructive interference?

A compact disk uses the interference of waves reflected from the CD to encode information. Light from a red laser (wavelength = 630nm) is reflected from small pits in the CD and waves from the bottom and top interfere. What is the minimum depth of the pit needed from destructive interference? Assume only air above the CD, and that the reflection occurs at a plastic coating with n = 1.6.

Since there is no phase shift between the rays the minimum thickness t = λ/4 where λ = λo/n

So t = 630nm/(1.6*4) = 98.4nm

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Mac Optical Drives

Apple manufactures various parts of computers. Optical drives are one of the products, manufactured by apple. Optical disks are a storage medium of data and optical drives are used to read and write these data on optical disks.

The optical disc consists of a ferromagnetic material sealed with a plastic coating. Optical drives have lasers that help to read and write the data in computer understandable forms. During reading, a laser beam projected on the disk and it reflects lights. The reflected light varies due to the magneto-optical Kerr effect.

During writing on the disk, the light becomes stronger so it can burn the disk in a single spot. This allows an electromagnet positioned on the opposite side of the disc to change the local magnetic polarization and data writes on disks.

There are various types of optical drives. These optical drives are:

CD-ROM:-CD-ROM stands for compact disk read only memory used to read data from disks. These drives enable to read data from audio cds, video cds and also mp3s. These drives read the data which already written/encoded on the disks. The data read on the disks are read by many times.

CD-RW: – CD-RW stands for compact disk writer. These drives have used to write the data on disks and also read the data which has written on disks. These drives enable to read data many times and also enable to write data many times depend upon the properties of disk that the properties of disk shows write once or write many. To write the data on CD, these drive use laser. Laser burn the data on disks as computer readable form.

DVD-ROM: – DVD-Rom are read only digital versatile disc drives that read the high capacity of storage data disks. These disks store the data minimum 4.7 gigabyte whereas the Cds store the data maximum 800 megabyte. These drives also read the data which already written/encoded on the disks. The DVD-ROM supports disks with capacities of 4.7GB to 17GB and access rates of 600 KBps to 1.3 MBps. The one specialty of DVD-ROMs is that these enable to read the data from CD disks also.

DVD-RW: – DVD-RW stands for digital versatile disc writer. These drives have used to write the data on DVD disks as well as CD disks and also read the data which has written on disks. These drives enable to read data many times and also enable to write data many times depend upon the properties of disk that the properties of disk shows write once or write many. To write the data on DVD disks, these drive use laser. Laser burn the data on disks as computer readable form.

Blu-Ray drives: – Blue ray drives are enable to read or write the data on disks that has the capacity of 50 gigabytes, 25 gigabyte capacity of each side. These disks are readable and writable on both sides.

DVDs are mainly used for video and not for software distributions. DVD drives are still backwards compatible with CD formats however. All optical drives are rated by speed that refers to the maximum speed the drive operates when compared to the original CD or DVD standards. There are many speeds of CD writers, which vary through 8x to 52x. A 24x drive may run up to 24x when writing.

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http://www.dvwarehouse.com/

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The internet is the best place to buy cheap computer parts. Due to increase in demand for many parts in many suppliers find it profitable to sell their products online. The online dealers have their websites, which offer information on the various types of Mac parts available for purchase.

About the Author

Author: Harry Johnson
For Listing visit http://www.dvwarehouse.com (Best Online Computer Store) Used Mac Computer You can visit http://www.sellamac.com The easiest & fastest way to sell your used Macs.