C1 Analogue and Digital Signals Student Work Book

C1 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.

Decimal Number / Binary Number
(a) / 8 / 01000
(b) / 4
(c) / 10100
(d) / 00110
(e) / 15
(f) / 28
(g) / 11001
(h) / 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.

(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.

(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 47.6mms-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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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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9). (a) The wavelength, in air, of the light used to read a DVD is 650nm. 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 22mm and the outer track is 58mm. 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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(d) In practice the minimum length of a island is 830nm. 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.

Prepare a presentation which you could deliver to local business leaders highlighting what you consider to be the three key issues facing society associated with the digital storage of information.

Attach a print out of your presentation to this booklet.

C1 Analogue and Digital signals – Student Work Book – Responses.

The following responses are intended to act as a guide for staff and students.

1). (a) Base 2 number system

(b) Enables circuits to represent numbers based on whether they are on or off, corresponding to 1 and 0

2).

Decimal Number / Binary Number
(a) / 8 / 01000
(b) / 4 / 00100
(c) / 20 / 10100
(d) / 6 / 00110
(e) / 15 / 01111
(f) / 28 / 11100
(g) / 25 / 11001
(h) / 19 / 10011

3). (a) Any wiggly line not going backwards in time.

(b) E.g. microphone, LDR, thermistor etc

4). (a) Any pulse waveform with a constant amplitude.

(b) CD, thermostat, switch etc

5). (a) C90 plays for 45 minutes each side = 2700s

=> 130/0.0476 = 2731s

(b) Mean radius of tape on spool is (26 + 12) / 2 = 19mm

=> Circumference of mean radius = 2p19 = 119.38mm

=> Number of circles of tape = 130/0.11938 = 1089

Now width of tape on spool = 26 – 12 = 14mm

=> Thickness of tape = 14 / 1089 = 0.0129mm

6). (a) Can be easily copied for back ups, does not degrade, can be encrypted etc

(b) Difficult to completely delete, easily copied etc

7). (a) Responses to this will have to adapt to technology. Currently examples might include:-

floppy disk = 1.44MB

CD = 700MB

DVD = 4.7GB

(b) 4000 / 5 » 800 music files

8). (a) See support materials

(b) On a spiral track as a series of bumps or islands (pits) representing binary numbers.

9). (a) 650 / 1.56 = 417nm

(b) For destructive interference the path difference should be l/2, so therefore the height of the island should be l/4. So island height is 417 / 4 = 104.25nm

10). (a) p582 - p222 = 9048mm2

(b) Mean radius of spiral = (58 + 22) / 2 = 40mm

Circumference of mean track is 2p40 = 251.33mm

=> Area of mean track is 251.33 × 0.0016 = 0.4mm2

=> Number of circular tracks = 9048 / 0.4 = 22620

=> Taking the mean circumference total length = 22620 × 251.33 » 5.685km

=> 5685 / 5872025600 = 0.968µm

(d) land region needed between the islands, error correction, block headers etc

11). Appropriate presentation dealing with the three key issues facing society associated with the digital storage of information.