5.2 - Data Storage - Optical Media Flashcards

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1
Q

Examples of optical storage devices (2)

A

CDs

DVDs

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2
Q

How CDs/DVDs work (5)

A

laser shone at disk

arm moves laser across disk surface

laser burns pits onto disk surface

laser reads the pits and lands on disk surface

reflected light from laser shining on disk is captured by sensor

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3
Q

Where is data stored on the spiral track (2)

A

pits on the spiral track

lands on the spiral track

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4
Q

What is used to read and write data on CDs/DVDs

A

a red laser

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5
Q

Physical Appearance of DVDs (3)

A

has 2 individual record layers

2 layers joined together with transparent polycarbonate spacer

very thin reflector sandwiched between two layers

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6
Q

What does the R mean after DVDs or CDs

A

data can only be read once

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7
Q

What does the letter RW mean after DVDs or CDs

A

data can be written to and read from the disk

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8
Q

DVD and CD differences

A

DVD has larger storage capacity

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9
Q

DVD laser type

A

650 nm red laser

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10
Q

CD laser type

A

780 nm red laser

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11
Q

DVD construction

A

2 0.6 mm polycarbonate layers

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12
Q

CD construction

A

one 1.2 mm polycarbonate layer

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13
Q

DVD track pitch (distance between each track)

A

0.74 micrometers

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14
Q

CD track pitch (distance between each track)

A

1.60 micrometres

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15
Q

What does a shorter wavelength of laser light mean

A

greater storage capacity

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16
Q

Difference between Blu-ray and DVDs (4)

A

Blue ray uses blue laser - shorter wavelength

shorter wavelength allows pits and lands to be smaller - stores 5 times more data than dvd

blu ray automatically comes with encryption

blu ray data transmission is faster than dvd - 36 Mbps to 10 Mbps

17
Q

storage capacity of dual-layer dvd

A

4.7 GB

18
Q

storage capacity of single layer blu ray

A

27 GB

19
Q

storage capacity of dual-layer blu ray

A

50GB

20
Q

Blu-ray applications (3)

A

record high definition tv programs

skip quickly to any part of disk

edit programmes on disk

20
Q

Wavelength of blu-ray laser

A

405 nm

21
Q

Track pitch of blu-ray

A

0.30 micrometres

22
Q

Construction of blu-ray single layer

A

1.2 mm polycarbonate layer

23
Q

Construction of blu-ray double layer

A

two 0.6 mm polycarbonate layer