SENIOR SCIENCE SUMMARY:

INFORMATION SYSTEMS1. INFORMATION SYSTEMS ARE MANY AND VARIED AND DEPEND ON THE TRANSFER OF ENERGY FROM PLACE TO PLACE

Overview

Forms of energy – light, sound, mechanical, electrical, heat, kinetic, potential, nuclear, chemical Waves carry energy; waves transmit energy from one place to another. Features of waves;

o Wavelength – distance between 2 peakso Frequency – number of waves past a certain pointo Amplitude – height of wave, loudness/softness

A changing magnetic field produces an electric field, the energy produced by these changing fields radiates out as waves called ELECTROMAGNETIC waves! e.g. Gamma rays, UV, radio, microwaves

Waves can be refracted (bent) or reflected (bounced off)

1.1 OUTLINE THE BASIC PATTERN OF THE INFORMATION TRANSFER PROCESS AS – CODE COMMON TO BOTH PARTIES – MESSAGE – TRANSMISSION OF CODED MESSAGE – DECODER

Every signal must be sent the same way each time One signal must be able to be distinguished from another signal, e.g. radio waves from microwaves There needs to be a system that can interpret & coordinate the information received

IDEA CODE TRANSMISSION DECODE FEEDBACK

Code common: E.g. pictures, words, music turn into codes to be a message

Message: Can be transferred electronically, usually digital

Transmission: Once carrier wave has been coded, it is sent to required destination. Use either (or both) an electric

current or EM waves to carry messages

Decoder: 1) Detects and separates the code from the carrier current or wave. 2) converting that code into a

form that the receiver’s senses can detect and interpret to make meaning.

Senior Science – By Natalie C 2014

1.2 IDENTIFY A RANGE OF INFORMATION SYSTEMS USED DAILY

• Words, music & images are transmitted around the world via cable (copper wire & optical fibre), microwave, radio & satellite-based communication systems.

1.3 CLASSIFY INFORMATION SYSTEMS AS—VERBAL & NON-VERBAL—SHORT DISTANCE & LONG DISTANCE—ELECTRONIC & NON-ELECTRONIC

Verbal – involves the use of WORDS, either spoken or as text Non-verbal – involves pictures, smell, touch, taste Short distance – occurs in the presence of the receiver or within the immediate area e.g. speech Long distance – communicating with people in other states/countries e.g. via satellite

Senior Science – By Natalie C 2014

1.4 RECALL PHENOMENA AND EVENTS WHERE DIFFERENT FORMS OF ENERGY ARE USED

Energy is involved when a change to the physical or chemical state of a material object occurs.Example:

Electricity is a phenomenon related to the movement of electricity charged particles. Batteries convert chemical (potential) energy to electrical energy.

Types of energy…

Chemical – energy stores in chemicals Potential – energy that can be released later Kinetic – movement energy Heat – energy from differences in temperature Light – energy from light Sound – energy released as noise Electromagnetic – energy carried as waves Electrical – energy carried by electrons Solar – energy from the sun Nuclear – energy released from atoms

1.5 IDENTIFY THE TRANSFORMATION OF ENERGY AT EACH STAGE OF INFORMATION TRANSFER IN THE FOLLOWING DEVICES—LAND CONNECTED TELEPHONES, MOBILE PHONES, TV, RADIOS, CD PLAYERS

LAND-CONNECTED TELEPHONES:

Contains microphone and small loudspeaker 2 wires connected to telephone; one is grounded and other carries a voltage that makes phone ring When headset is lift switch connects 2 wires through microphone dial tone to loudspeaker

Sound electrical sound

MOBILE PHONES:

Are self-contained transmitters and receivers of radio waves

Transmitter (towers) picks up radio waves Microwaves are also used to relay

transmission of the message

Senior Science – By Natalie C 2014

Sound Electrical Radio waves Transmitted via microwaves Electrical Sound

TELEVISION:

Transforms light energy (visual) into electrical energy transmits the TV signal as an EM wave Converted to kinetic energy of electrons to strike the TV screen

Light & Sound Electrical EM radiation Electrical Kinetic Light & Sound

RADIOS:

Microphone converts sound energy into electrical energy Then radio waves carry this energy where the electrical energy is converted to sound by a

loudspeaker

Sound Electrical Radio waves Electrical Sound

CD PLAYERS:

Stores information digitally (codes, binary) Use laser light to read coded message Digital signals are converted to original signal,

amplified & converted to sound by speaker. Light energy is the DECODER

Sound Electrical Sound

1.6 DISCUSS THE ADVANTAGES OF USING A RANGE OF INFORMATION SYSTEMS

Information transferred at speed of light e.g. via satellite to TV, radio, computers, telephones Reaches a wide audience through TV e.g. mass audience Digital information can be received immediately Video conferencing – communicate without travelling, saving time and money

Senior Science – By Natalie C 2014

Greater mobility and more compact e.g. mobile phones Access to a choice of systems is more reliable Sound systems can be a warning system Cheaper and high quality Personal/confidentiality – phones

2. ELECTROMAGNETIC RADIATION CAN BE MODULATED TO CARRY DIFFERENT TYPES OF INFORMATION

Longer the wavelength, travel very far but not strong

Shorter the wavelength, the more strength (BUT doesn’t travel long distances)

2.1 IDENTIFY THE TYPES OF WAVES IN THE EM SPECTRIUM CURRENTLY USED FOR COMMUNICATION SYSTEMS AS—VISIBLE LIGHT, INFRA-RED, MICROWAVES, RADIO WAVES(TV, AM, FM)

EM refers to waves of energy which are caused by the varying motions of charged particles. EM waves do NOT need a medium such as air through which to travel. Parts of the EM spectrum used for communication – visible light, infrared, microwaves, radio

waves (AM & FM)

Uses for EM waves in communication Basic facts

Radio waves – radio, TV Microwaves – mobile phones, Wi-Fi Infra-red – remote controls for TV, stereos,

cordless computer devices Visible light – optical fibres, telephone

Radio waves have the lowest energy. All EM waves travel at the speed of light. As wavelength decreases, frequency

increases.UHF: ultra-high frequency and VHF: very high

frequency

Senior Science – By Natalie C 2014

2.2 COMPARE THE ADVANTAGES & DISADVANTAGES OF USING MICROWAVES & RADIO WAVES IN COMMUNICATION TECHNOLOGIES

RADIO WAVES:Advantages Disadvantages

o Can be transmitted in space can reach longer distances

o Do NOT require line-of-sight transmissiono Reflects off objects on Earth can reach

remote placeso Can travel further at night

o Can be absorbed by water, oxygen, carbon dioxide in atmosphere

o Affected by static, over power lines and lightning

o Require more electrical power for transmission than microwaves

o Heavy rainfall absorbso Same signal can arrive at different time

“ghost effect”

MICROWAVES:

Advantages Disadvantageso Different bandwidth to radio waves no

crowdingo Do not spread out very much minimal

energy is wastedo Possible to send more than one signal out at

onceo High frequency more information

transmittedo Can be reflectedo Requires less electricity

o Travel in straight lines require line-of-sight

o May be blocked by hills, buildings, mountains

o Water molecules tend to absorb themo Signals must be relatively strong for

information to transfer

2.3 IDENTIFY COMMUNICATION TECHNOLOGIES THAT USE ENERGIES FROM THE EM SPECTRUM FOR COMMUNICATION PURPOSES

Senior Science – By Natalie C 2014

3. EM WAVES HAVE DIFFERENT PROPERTIES WHICH ARE UTILISED IN A RANGE OF COMMUNICATION SYSTEMS THROUGH AIR AND SPACE

3.1 IDENTIFY THAT WHERE INFORMATION SYSTEMS CANNOT BE PHYSCIALLY LINKED THE INFORMATION MAY BE TRANSMITTED IN WAVE FORM THROUGH THE ATMOSPHERE OR SPACE

The first type of long distance without wires used RADIO WAVES, which can travel in a direct straight line, can be bounced off the upper layers of the earth’s atmosphere.

Transmitting antenna produces waves that travel through air or space at great speed and over a range of distances

Receiving antenna tuned to particular frequencies will detect the signal and relay this to the receiving communication device

Places where communication by physical links (e.g. wires) is NOT practical or possible include –space, airplanes, ships

Locations where rapid and/or long distance communication was made possible by radio include – ship-to-ship, airplane pilots, international communication

3.2 IDENTIFY THE PROPERTIES OF ENERGY FROM THE EM SPECTRIUM THAT MAKE IT USEFUL IN COMMUNICATION TECHNOLOGIES INCLUDING—SPEED OF TRAVEL, ABILITY TO TRAVEL IN A STRAIGHT LINE, ABILITY TO BE REFLECTED

EM waves travel at the speed of light (300,000km/s) allowing for long distance communication EM waves travel in straight lines allowing a beam of radiation to be produced improving range &

long distance communication EM waves spread out from a point source for broadcasting, mass communication EM waves do NOT require a medium in which to travel allowing for communication into space EM waves can be;

o reflected – direction can be changedo diffracted – allowing them to be bent around objects

The LONGER the WAVELENGTH, the SHORTER the FREQUENCY!

3.3 DESCRIBE THE INDIVIDUAL PROPERTIES OF VISIBLE LIGHT, RADIO WAVES(AM, FM, TV) AND MICROWAVES AND RELATE THESE TO THEIR USE IN COMMUNICATION SYSTEMS

VISIBLE LIGHT:

Light (having most high frequency) has huge information carrying capacity Light can be refracted and reflected to achieve total internal reflection. Optical fibres are used to transmit light pulses generated by an electrical. The use of the fibre

ensures privacy and an energy efficient way of sending information.

e.g. bar codes, fax, optic fibres

Senior Science – By Natalie C 2014

Visible light diagram:

MICROWAVES:

Microwaves travel in straight lines line-of-sight High frequency large carrying capacity Easily absorbed and scattered in the atmosphere – they need directional aerials for transmission

and reception (to ensure sufficient signal strength) Can easily pass through rain, smoke, fog and they also pass through the ionosphere and space

e.g. mobile phones, TV, satellite communication

RADIO WAVES – AM:

AM radio waves reflect off layers of the atmosphere i.e. ionosphere and are rounded “radical waves” which allows them to be transmitted out-of-sight. This gives AM radio very long range.

Relatively low frequency carry small amounts of information Can travel through almost any medium e.g. underwater, buildings, mines

RADIO WAVES – FM:

Much higher frequency than AM radio waves carry more information

Shorter wavelength do not diffract well around large objects

FM radio waves spread out from a point source for broadcasting

Do NOT reflect of the ionosphere must be line-of-sight

RADIO WAVES – TV:Senior Science – By Natalie C 2014

Use VHF and UHF waves (very high, ultra high) Both VHF and UHF waves spread out from point source i.e. the aerial for broadcasting Travel at speed of light fast communication Weak signals can occur as buildings & hills absorb waves UHF travel in straight lines useful for crowded urban areas (good reflection)

VHF used for FM radio, TV, marine radioUHF used for TV, police radio

4. GEOSTATIONARY SATELLITES RELAY AND TRANSMIT INFORMATION FROM THE OTHER SIDE OF THE WORLD

A communication satellite is essentially a microwave relay station in earth orbit.

The signal sent to the satellite is called the up-link; the signal sent from the satellite to the earth is

called the down-link.

Power from the transponder comes from on board batteries charged by solar panels.

Large, highly directional parabolic antennae are pointed at the satellite and used to send and

receive signals. This device is called a transponder.

Most modern telecommunications satellites are placed in a geostationary orbit, 36 000 km above

the equator.

The area of the earth that can communication with satellite is called the satellite’s footprint.

4.1 EXPLAIN WHY THE SATELLITE MUST BE AT A HEIGHT WHERE ITS REVOLUTION PERIOD IS THE SAME AS THAT OF THE EARTH’S PERIOD OF ROTATION

A geostationary satellite is one that orbits the Earth once every 24 hours, and therefore remains over the same point in the Earth at all times.

This is because so it stays in the same spot at all times – the satellite and point on earth – for RECEPTION

The satellite dish must face the same direction at all times to ensure that signals are received and retransmitted.

Senior Science – By Natalie C 2014

Comparing geostationary and low-earth orbit satellites:

Geostationary satellites Low-earth orbit satellite High altitude – 36 000km above equator Covers 80% of earth These satellites remain above the same

point on the equator at ALL times Good for communications or weather

forecasting satellites 3 geostationary satellites exist

Low altitude – 500 to 1500km Covers other 20% of earth Many low earth satellites must be used – approx. 15 Commonly used for high resolution land imagery and

mobile telecommunications e.g. mobiles, ships, airplanes

Because these satellites are so close to earth, there is no time delay in information transmission

4.2 EXPLAIN WHY EARTH-BASED SATELLITE DISH MUST ALWAYS FACE THE GEOSTATIONARY SATELLITE COMMUNICATING WITH IT

Senior Science – By Natalie C 2014

A satellite dish must face the same direction and must remain at the same location with respect to the surface of the earth.

This is because the satellite dish is aimed a particular satellite.

The satellite the dish is in contact with is always in the same relative position in sky.

The parabolic shape of the dish focuses the signals into the central point.

5. INFORMATION CAN BE TRANSMITTED IN THE FORM OF ELECTRICAL IMPULSES

5.1 IDENTIFY COMMUNICATION TECHNOLOGIES THAT TRANSFORM ONE TYPE OF ENERGY INTO ELECTRICAL ENERGY

Communication technology Type of energy transformed into electrical energyMicrophone Sound

Radio Sound TV camera Light

Scanner LightKeyboard Kinetic

Receiving antenna EM radiation in radio frequency

5.2 DESCRIBE THE TRANSMISSION OF IMAGES USING DIGITAL TECHNOLOGIES IN TERMS OF SCANNING OF THE INPUT IMAGE ALONG VERY THIN LINES

The piece of electronic behind most modern imaging devices is the charge-coupled device. This is a large integrated circuit designed to RECORD images. The chip is divided up into millions of tiny squares called pixels.

Laser light ‘scans’ image in very thin lines image is stored in analog form charge-coupled

device converts it to a digital signal (BINARY CODE) transmitted using telephone cables (fax machine) receiver converts digital signal back to

analog image is received!

Fax machine forms of energy:

Senior Science – By Natalie C 2014

Light energy electrical energy binary code sensor voltage

5.3 EXPLAIN HOW THE CODING OF THE IMAGE INTO A SERIES OF ZEROS AND ONES ALLOWS ITS TRANSMISSION AND ULTIMATE DECODING

Electronic digital devices work by digitalising an image i.e. dividing it into a grid of dots. Each dot is represented by a BIT that has a value of either 0 or 1. Images and data are converted to a series of 1’s and 0’s (digitalised) to be transmitted on the

RECEIVING end, a device reads the incoming data (as a binary code), translates the 0’s and 1’s, back into dots (the image)

Binary digits can be represented and/or transmitted as voltages or as pulses or light ∴ WIRE OR OPTICAL FIBRE

The coding of a signal into a series of 0’s and 1’s allows its transmission and ultimate decoding because an accurate record of the original signal can be made using digits (0, 1)

6. ELECTRICAL ENERGY CAN BE CONVERTED TO LIGHT ENERGY FOR USE IN OPTICAL FIBRE COMMUNICATION SYSTEMS

Overview:

Glass and plastic fibres as thin as a few micrometres in diameter can be used to transmit light with very little loss of intensity.

‘Leaking’ of light in optical fibres ‘crosstalk’ which leads to loss of information and a shorter distance of transmission

The speed of light depends on the refractive index;o The higher the refractive index, the faster light travels (compared to lower

refractive index) Most optical fibres used in long distance, high speed communication have a very thin core. These

are called single-mode fibres.

6.1 OUTLINE PROPERTIES OF OPTICAL FIBRES AS COMMUNICATION CARRIERS

Senior Science – By Natalie C 2014

An optic fibre consists of 2 sections with a covering;o Glass core – runs through the centre of the strando Glass cladding – surrounds the core

Properties of optical fibres as communication carriers;

The main job of an optical fibre is to guide light with minimum loss of signal Made from very pure, almost mineral-free glass allows for long distance transmission of light Cable is flexible and can be easily bent can be bent around obstacles without need for relay

(reflection) devices Total internal reflection light is transmitted with very little loss of energy over long distances Travels at 2/3 speed of light in a vacuum makes communication using optic fibre VERY fast Attenuation is the loss of signal strength—there must be some loss of signal strength in an optical fibre

Two types of optical fibresSingle-mode fibre Multi-mode fibre

Extremely thin cores Designed to force the light to travel in a

single mode They accept light only along the axis of the

fibres need laser light

Larger cores than single-mode fibres They accept light from a variety of angles Loses more signal

∴ An optical fibre cable is a technology that uses glass (or plastic) threads (fibres) to transmit data via light. They are a network of glass cables insulated cladding.

6.2 OUTLINE THE PRINCIPLE OF TOTAL INTERNAL REFLECTION AND RELATE THIS TO THE ADVANTAGES OF FIBRE OPTICS OVER MORE CONVENTIONAL CARRIERS OF INFORMATION

Senior Science – By Natalie C 2014

The glass in the cladding is optically less dense than the core glass. As such, the cladding glass has a lower refractive index. This causes the cladding to act as a mirror for light travelling in the core. As a result, the light (infrared) travels through the core by a series of continuous reflections TOTAL INTERNAL REFLECTION.

Optical fibre technology depends on the property of total internal reflection. When light is passed from one substance to another, its path is refracted (bent). The amount of

light is bent between 2 materials is measure by the refractive index.o Glass (dense) higher refractive indexo Air lower refractive indexo And therefore, light travels faster through AIR than through GLASS!

Total internal reflection occurs when light travels from a more-dense to a less-dense medium (e.g. glass to air)

The greater the angle of incidence (starting angle of light), the greater the critical angle (end result)

TOTAL INTERNAL REFLECTION

Senior Science – By Natalie C 2014

Total internal reflection ONLY occurs when…

1. The rays of light must travel from a dense medium to a less dense medium.

2. The angle of incidence must be greater than the critical angle.

6.3 & 6.5 OUTLINE THE DIFFERENCES AND RELATIVE MERITS IN THE USE OF FIBRE OPTIC CABLES AND METAL CABLES TO TRANSMIT AND RECEIVE INFORMATION

Advantages of optic fibre over copper wires: Greater bandwidth carry more data Not affected by radio waves – no static Thinner and lighter Less susceptible to corrosion longer lifespan Can carry digital and analog information More secure Can stretch further and overall cost cheaper

Disadvantages of optic fibre over copper wires:o Very expensive to installo More fragile than wire o Repeaters need to be added to boost signal strengtho Optic fibres require coatings

Type of cable Carrying capacity Cost per km Rate of information transfer

Security

Optic fibre Large carrying capacity (several GB of data per

Very expensive (but prices are dropping)

10 GB/s High security as it optic fibre is harder to tap into and be

Senior Science – By Natalie C 2014

second) intercepted Copper wire Small carrying

capacityCheap because new technology is being introduce

2MB/s Low security as EM radiation is emitted from copper cables this can be detected and decoded

Senior Science – By Natalie C 2014