1. Current technologies associated with information transfer may use waves of one form or another Soundtrack: Bitter Sweet Symphony images from SciArt.

1. Current technologies associated with

information transfer may use waves of one form or another

Soundtrack: “Bitter Sweet Symphony”

images from SciArt

Describe the energy transformations required in one of the Describe the energy transformations required in one of the following:following:

– fixed telephone– fixed telephone – mobile telephone– mobile telephone – fax/modem– fax/modem– radio and television– radio and television– information storage systems– information storage systems

e.g. Transmitting avoice messageon a mobile phone:

SOUND ENERGY

ELECTRICALENERGY

ELECTROMAGNETICRADIATION

(RADIO WAVES)

Waves are a transfer of energy Waves are a transfer of energy disturbance that may occur in one, disturbance that may occur in one, two or three dimensions, depending two or three dimensions, depending on the nature of the wave and the on the nature of the wave and the

mediummedium

what wavelength is 96.1 MHz???????

Given s vs t and s vs x can we work out v?

for one source, f does not change when medium does

images from SciArt

Mechanical waves require a medium for propagation while electromagnetic waves do not!

images from Microsoft Encarta

Describe the relationship between particle motion and the direction of Describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves energy propagation in transverse and longitudinal waves

They move well through solids and on the surface of liquids but not through liquids or gases because of loose bonds between particles

images from SciArt

2. Sound waves can be used to illustrate many of 2. Sound waves can be used to illustrate many of thethe

properties of waves that are utilised in properties of waves that are utilised in communication technologiescommunication technologies

discuss the effect of density of the medium on the transmission speed of sound waves

The velocity of sound in many other gases depends only on their density. If the molecules are heavy, they move less readily, and sound progresses through such a medium more slowly Sound generally moves much faster in liquids and solids

than in gases. In both liquids and solids, density has the same effect as in gases; that is, velocity varies inversely as the square root of the density.

images from SciArt

Relate compressions and rarefactions of sound waves Relate compressions and rarefactions of sound waves to the crests and troughs of transverse wavesto the crests and troughs of transverse waves

Explain qualitatively that pitch is related to frequency and volume to amplitude of

sound waves

Sonar, acronym for SOund Navigation And Ranging, a detection system based on the reflection of underwater sound waves— just as radar is based on the reflection of radio waves in the air. Distance is worked out from t assuming constant v in water

describe the effect of different materials on the describe the effect of different materials on the reflection and absorption of soundreflection and absorption of sound

describe the transfer of energy involved in the describe the transfer of energy involved in the absorption of soundabsorption of sound

images from SciArt

Describe the principle of superposition and compare Describe the principle of superposition and compare the resulting waves to the original waves in soundthe resulting waves to the original waves in sound

3. Recent technological developments have 3. Recent technological developments have allowed greater use of waves in the allowed greater use of waves in the

electromagnetic spectrum that do not electromagnetic spectrum that do not require a medium for propagationrequire a medium for propagation

Electromagnetic radiation has some everyday uses and effects, including applications in communication technology

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Electromagnetic radiation exists at arange of different frequencies andwavelengths - -a whole SPECTRUM!

Identify some methods of detection for a number of Identify some methods of detection for a number of wave bands from the electromagnetic spectrumwave bands from the electromagnetic spectrum Explain that the penetrating power Explain that the penetrating power of electromagnetic waves of electromagnetic waves is related to differences in frequency or wavelengthis related to differences in frequency or wavelength

Explain that the relationship between the intensity Explain that the relationship between the intensity of electromagnetic radiation and distance from a of electromagnetic radiation and distance from a source (for a large distance) is an example of the source (for a large distance) is an example of the

inverse square lawinverse square lawI prop. to 1/d I prop. to 1/d

Outline how the modulation of amplitude or frequency of visible light, microwaves and/or radio waves can be used to transmit information

Discuss limitations of the use of electromagnetic waves for communication purposes

AMPLITUDEMODULATION

FREQUENCYMODULATION

Low frequency electromagnetic radiation penetrates the atmosphere better than high

frequency. e.g. sunsets look red because youare looking at the light through more atmosphere

e.g. eye or photographic film

for light,thermometer for

infra-red,Geiger counter

for Gamma rays

Electromagnetic radiation of different wavelengths is absorbed by different amounts in the atmosphere. Wavebands which are absorbed are therefore not easily detected from ground-based systems, so space telescopes (such as the Hubble Space Telescope) are preferable.

So only near-UV, visible light, near-Infrared, radio and microwavesmake it to the ground with out much absorption by the atmosphere.

All others are more easily detectable from space

describe ways in which applications of reflection of light, radio waves and microwaves have assisted in information transfer

4. Many communication 4. Many communication technologies use applications of technologies use applications of

reflection and refraction of reflection and refraction of electromagnetic waveselectromagnetic waves

ANGLE OF INCIDENCE=ANGLE OF REFLECTION

Describe one application of reflection for Describe one application of reflection for each of the following:each of the following:

plane surfaces

concave surfacesconvex surfaces

Radio waves can diffract around objects and are reflected by the ionosphere and the ground, so they could be sent around the world even before there were satellites. However, reliability depends on the time of the day, the position of the sun, solar winds and losses of intensity over distance.

images from SciArt

Describe refraction in terms of the Describe refraction in terms of the bending of the wavefront passing bending of the wavefront passing

from one medium to anotherfrom one medium to another

Explain that refraction is related to Explain that refraction is related to the different velocities exhibited by the different velocities exhibited by

a wave in two mediaa wave in two media

images from SciArt

Define refractive index in terms of changes in the velocity of a wave in Define refractive index in terms of changes in the velocity of a wave in passing from one medium to anotherpassing from one medium to another

Define and discuss the application of Snell’s Law:Define and discuss the application of Snell’s Law:

v1/v2 v1/v2 (sin i)/(sin r) (sin i)/(sin r) = refractive index = refractive index

Identify the conditions necessary for total internal reflection and determine critical angleOutline how refraction and/or total internal reflection are used in technologies such as lenses or optical fibres

5. Other properties of electromagnetic 5. Other properties of electromagnetic waves have potential for future waves have potential for future

communication technologies and data communication technologies and data storage technologiesstorage technologies

Identify types of communication data that are stored or Identify types of communication data that are stored or transmitted in digital formtransmitted in digital form

Discuss the developments in technology that allowed Discuss the developments in technology that allowed the production of communication technologies, such as the production of communication technologies, such as

CD technology and Global Positioning SystemsCD technology and Global Positioning Systems

e.g. CDs use electromagnetic radiation (laser light) to reflect off pitsin the CD surface. The intensity of the reflected light provides a varying signal which is changed to a binary code of numbers whichcan be used to create the signal amplitude of the music or video.