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

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

1 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 following: – fixed telephone– mobile telephone– fax/modem – radio and television– information storage systems Describe the energy transformations required in one of the following: – fixed telephone– mobile telephone– fax/modem – radio and television– information storage systems e.g. Transmitting a voice message on a mobile phone: SOUND ENERGY ELECTRICAL ENERGY ELECTROMAGNETIC RADIATION (RADIO WAVES)

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

3 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

4 Mechanical waves require a medium for propagation while electromagnetic waves do not! images from Microsoft Encarta

5 Describe the relationship between particle motion and the direction of 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

6 2. Sound waves can be used to illustrate many of the properties of waves that are utilised in communication 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

7 Relate compressions and rarefactions of sound waves to the crests and troughs of transverse waves Explain qualitatively that pitch is related to frequency and volume to amplitude of sound waves

8 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

9 describe the effect of different materials on the reflection and absorption of sound describe the transfer of energy involved in the absorption of sound describe the effect of different materials on the reflection and absorption of sound describe the transfer of energy involved in the absorption of sound images from SciArt

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

11 3. Recent technological developments have allowed greater use of waves in the electromagnetic spectrum that do not require a medium for propagation Electromagnetic radiation has some everyday uses and effects, including applications in communication technology images from SciArt Electromagnetic radiation exists at a range of different frequencies and wavelengths - - a whole SPECTRUM!

12 Identify some methods of detection for a number of wave bands from the electromagnetic spectrum Explain that the penetrating power of electromagnetic waves is related to differences in frequency or wavelength Identify some methods of detection for a number of wave bands from the electromagnetic spectrum Explain that the penetrating power of electromagnetic waves is related to differences in frequency or wavelength Explain that the relationship between the intensity of electromagnetic radiation and distance from a source (for a large distance) is an example of the inverse square law I prop. to 1/d Explain that the relationship between the intensity of electromagnetic radiation and distance from a source (for a large distance) is an example of the inverse square law 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 AMPLITUDE MODULATION FREQUENCY MODULATION Low frequency electromagnetic radiation penetrates the atmosphere better than high frequency. e.g. sunsets look red because you are looking at the light through more atmosphere e.g. eye or photographic film for light, thermometer for infra-red, Geiger counter for Gamma rays

13 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 microwaves make it to the ground with out much absorption by the atmosphere. All others are more easily detectable from space

14 describe ways in which applications of reflection of light, radio waves and microwaves have assisted in information transfer 4. Many communication technologies use applications of reflection and refraction of electromagnetic waves ANGLE OF INCIDENCE=ANGLE OF REFLECTION

15 Describe one application of reflection for each of the following: Describe one application of reflection for each of the following: plane surfaces concave surfaces convex 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

16 Describe refraction in terms of the bending of the wavefront passing from one medium to another Explain that refraction is related to the different velocities exhibited by a wave in two media Describe refraction in terms of the bending of the wavefront passing from one medium to another Explain that refraction is related to the different velocities exhibited by a wave in two media images from SciArt

17 Define refractive index in terms of changes in the velocity of a wave in passing from one medium to another Define and discuss the application of Snells Law: v1/v2 (sin i)/(sin r) = refractive index Identify the conditions necessary for total internal reflection and determine critical angle Outline how refraction and/or total internal reflection are used in technologies such as lenses or optical fibres

18 5. Other properties of electromagnetic waves have potential for future communication technologies and data storage technologies Identify types of communication data that are stored or transmitted in digital form 5. Other properties of electromagnetic waves have potential for future communication technologies and data storage technologies Identify types of communication data that are stored or transmitted in digital form

19 Discuss the developments in technology that allowed the production of communication technologies, such as CD technology and Global Positioning Systems e.g. CDs use electromagnetic radiation (laser light) to reflect off pits in the CD surface. The intensity of the reflected light provides a varying signal which is changed to a binary code of numbers which can be used to create the signal amplitude of the music or video.


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