1. distance = speed x time d = v t

2. Speed of sound

3. 340 m/s

4. Speed of light

5. 300,000,000 m/s

6. transmitter

7. sends signals

8. receiver

9. replays signals

10. microphone energy change

11. microphone Sound electrical

12. loudspeaker energy change

13. loudspeaker electrical sound

14. frequency Number of waves per second

15. Amplitude Wavelength

16. High frequency

17. Low frequency

18. High amplitude

19. Low amplitude

20. wave speed v

21. speed = frequency x wavelength v = f

22. Radio waves Same speed as light

23. Aerial Detects radio waves

24. Tuner Selects one frequency

25. Decoder Separates the audio signal from the carrier wave

26. Amplifier Increases amplitude of signal

27. Electricity supply Provides energy to amplifier

28. Loudspeaker Changes electrical signal to sound

29. Radio Transmission Radio frequency wave combined with audio frequency wave

30. Radio Transmission This is called amplitude modulaton

31. Amplitude modulation audio radioa.m.

32. Diffraction Bending round obstacles

33. Diffraction Long wavelength, low frequency bends more than short wavelength, high frequency

34. Television aerial decoder (vision) tuner amplifier TV tube decoder (sound) amplifier Loudspeaker

35. Television Line build-up moving backwards and forwards Lines made by electron beam across screen The lines build up to make picture

36. Television Brightness variation Dark areas – few electrons Light areas – many electrons

37. Television Image retention Eye retains image for short time 25 pictures per second – pictures seen as moving smoothly

38. Colour television Three electron guns One to hit red dots One to hit blue dots One to hit green dots

39. Colour television Colour mixing Red + Blue = Magenta Blue + Green = Cyan Green + Red = Yellow Blue+Green+Red = White

40. Colour television Colour mixing red blue green yellowcyan white magenta

41. Reflection Angle of incidence i r i = r mirror Angle of reflection =

42. Refraction airglass

43. Total Internal Reflection ir Above a certain angle (the critical angle), the light is reflected.

44. Optical Fibres i Used to carry telephone signals. Signal travels at 200,000,000 m/s r

45. Optical Fibres i Advantages (compared to wires) r Cheaper, lighter, carry more signals little energy loss

46. Satellites The higher the satellite The longer its period (time for one revolution round the Earth)

47. Satellites Geostationary satellite Takes 24 hours to make one revolution (stays above same point on Earth’s surface)

48. Curved Reflectors Large area collects more energy concentrates signal on detector

49. Curved Reflectors Curved reflector Receiver at the focus

50. Curved Reflectors Curved reflector transmitter at the focus