1. Electromagnetic spectrum

2. Learning today – copy The main features and characteristics of the Electromagnetic spectrum The uses and dangers of EM spectrum

3. Electromagnetic spectrum Mini-book – Due 17 th September One type of EM wave for each page Each page should contain the wavelength Each page should contain uses and other interesting information (including dangers) Attractive to look at (and funny?)-

4. The EM spectrum is a continuous spectrum

5. Visible light

6. λ ≈ 700 nmλ ≈ 420 nm

7. Ultraviolet waves λ ≈ 700 - 420 nm

8. Ultraviolet waves λ ≈ 700 - 420 nmλ ≈ 10 – 100 nm

9. X-rays λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm

10. X-rays λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm

11. Gamma rays λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm

12. Gamma rays λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001 – 0.00001 nm

13. Infrared waves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001 – 0.00001 nm

14. Infrared waves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m

15. Microwaves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m

16. Microwaves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m λ ≈ 10 -2 - 10 -3 m

17. Radio waves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m λ ≈ 10 -2 - 10 -3 m

18. Radio waves λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m λ ≈ 10 -2 - 10 -3 m λ ≈ 10 -1 - 10 3 m

19. Electromagnetic spectrum λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 0.001-0.00001nm λ ≈ 10 -4 - 10 -6 m λ ≈ 10 -2 - 10 -3 m λ ≈ 10 -1 - 10 3 m

20. Electromagnetic spectrum Long Wavelength Short Wavelength

21. Electromagnetic spectrum Long Wavelength Short Wavelength Low Frequency High Frequency

22. What do they all have in common? λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm λ ≈ 1 – 0.01 nm λ ≈ 10 -12 - 10 -14 m λ ≈ 10 -4 - 10 -6 m λ ≈ 10 -2 - 10 -3 m λ ≈ 10 -1 - 10 3 m

23. What do they all have in common? copy please They can travel in a vacuum They travel at 3 x 10 8 m.s -1 in a vacuum (the speed of light) They are transverse They are electromagnetic waves (electric and magnetic fields at right angles to each oscillating perpendicularly to the direction of energy transfer)

24. What else do you need to know?

25. Electromagnetic spectrum Long Wavelength Short Wavelength Low Frequency High Frequency

26. Uses of microwaves Satellite TV and cellular phones

27. Uses of Infrared waves Remote controls for TVs and intruder alarms

28. Uses of X-rays Medicine and security

29. Dangers of microwaves and X- rays

30. You need top know the speed of light (c) 300 000 000 m/s 3 x 10 8 m/s

31. Mini-book

32. Finish for homework. Due Thursday 21st June 2012

33. Electromagnetic spectrum Mini-book One type of EM wave for each page Each page should contain the wavelength Each page should contain uses and other interesting information (including dangers) Attractive to look at (and funny?) Due Thursday 21 st June.

34. Analogue and digital signals –copy Communication signals may be analogue or digital. Analogue signals vary continuously in amplitude between zero and some maximum level. Digital signals only have two voltage levels, for example +5V and 0V.

35. Learning today – copy Analogue and digital signals The uses and dangers of EM spectrum

36. Examples of analogue and digital systems ANALOGUEDIGITAL

37. Advantages of using digital signals- copy 1. Less interference than with analogue signals. Interference causes a hissing noise with analogue radio. This does not happen with digital signals because regenerator circuits are used to clean ‘noisy’ pulses. So a digital signal has a higher quality than an analogue one. Regenerator ‘Noisy’ pulse in ‘Clean’ pulse out

38. 2. Much more information can be sent. Copy Digital pulses can be made very short so more pulses can be carried each second. Different signals can be sent together by a process called multiplexing. 3. Digital signals are easily processed by computers.Copy Computers are digital devices!