14.1 Analogue and Digital signals – Student Work Book.
1).
(a)
Explain what is meant by the Binary number system.
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(b)
Explain why the binary number system is very important for digital electronic systems.
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2).
The table below contains both decimal and binary numbers.
Complete the table by giving the equivalent binary or decimal number.
The first row is completed for you as an example.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Decimal Number
8
4
Binary Number
01000
10100
00110
15
28
11001
19
For more examples go to www.ikes.freeserve.co.uk/homework/hwk.htm
3).
(a)
On the axes below, draw an example of an analogue signal.
voltage
time
(b)
State two examples of sources of analogue signals.
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4).
(a)
On the axes below, draw an example of a digital signal.
voltage
time
(b)
State two examples of sources of digital signals.
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5).
(a)
Show, by calculation, that if the tape speed of a C90 Compact Cassette was 47.6 mms-1
then there would be approximately 130m of tape in the cassette.
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(b)
When all of the tape is spooled onto the one reel, its outer radius is 26mm and its inner
radius is 12mm. Estimate, by calculation, the thickness of the tape.
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6).
(a)
Explain two advantages of storing information digitally.
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(b)
Explain one disadvantage of storing information digitally.
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7).
(a)
State three devices which can store digital information and give their approximate
capacity.
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(b)
A typical portable digital storage device has a capacity of 4GB. If average size of an
MP3 music file is 5MB, estimate, by calculation, how many music files can be stored on this device.
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(c)
How many CDs would be required to hold the same amount of information?
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8).
(a)
Draw a labelled diagram to represents the vertical cross-section through a CD.
(b)
Explain briefly how information is stored on a CD.
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(c)
Explain why a DVD will store more information than a CD even though they are
physically the same size.
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9).
(a)
The wavelength, in air, of the light used to read a DVD is 650 nm. If the refractive index
of the polycarbonate coating on the bottom of a DVD is 1.56, calculate the wavelength
of the
light in the polycarbonate coating.
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(b)
If destructive interference is to occur with the light reflected from an island on a DVD,
calculate the height of the island.
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10).
(a)
The radius of the inner track on a CD is 22 mm and the outer track is 58 mm. Calculate
the area of the CD that is used for storing data.
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(b)
If the spiral tracks are 1.6µm apart, estimate the length of the spiral that is used to store
the data.
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(c)
If 700MB of data is to be stored on a CD, estimate the minimum length of an island.
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(d)
In practice the minimum length of a island is 830 nm. Why is this value smaller than the
calculated value in part (c).
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11).
The storage of information digitally is causing many issues including those listed below:Storage, Cataloguing, Moral, Ethical, Piracy, Data centres, Waste and Back up of data.
Think about the issues, which you could relate to local business leaders highlighting what you
consider to be the three key problems facing society that are associated with the digital storage of
information.