Lesson Objectives: The electromagnetic spectrum: To know the parts of To know their properties, uses, dangers

Transcription

1 03/02/2014 Electromagnetic Spectrum Review Using Waves Lesson Objectives: The electromagnetic spectrum: To know the parts of To know their properties, uses, dangers To compare and contrast analogue and digital signals Key Words: Binary Fluoresence

2 The Electromagnetic Spectrum

3 Properties of EM Waves They transfer energy They are transverse waves They can be reflected, diffracted and refracted They can travel through a vacuum at 3 x 10 8 m/s The shorter the wavelength, the more dangerous they are

4 Radio Waves Can you spot a trend: wavelength V usage?

5 The figure shows electromagnetic waves used to send signals from a transmitter.

6 Microwaves Where does the name come from? Where are microwaves on the electromagnetic spectrum? What are typical wavelengths for microwaves? Can microwaves interfere with radio waves? What can you use to stop microwaves? Is heating food in a plastic bowl a silly idea? What do we use microwaves for? Are mobile phone masts dangerous? How can mobile phone signal loss occur? How does cooking with a microwave differ to with a toaster or an oven?

7 IR Mind Map Infra Red

8 Now over to you! What is the wavelength of my laser pen? It has a frequency (f) of 5.64 x Hz

9 03/02/2014 Brainstorm Time Where does UV come from? What are the uses/dangers?

10 How are X-rays produced?

11 How does matter decay? When a radioactive nucleus decays spontaneously, the nucleus ejects out bits of itself ( alpha_ particles or _electrons ) or alternatively gamma rays.

12 UCL

13 Digital and Analogue Signals By the end of the lesson you should be able to: Distinguish a digital from an analogue signal Understand why TV is going digital Key Words: Noise Regenerate Binary Byte -Write down today s title, lesson objectives, key words and the date 03/02/2014 -Underline all of your work

14 By the end of the lesson: are you... Confident about what analogue and digital waves are Able to explain how a carrier wave and signal wave are used to transmit a message state three advantages of digital explain why digital signals are less noisy

15 Which are analogue and which are digital?

16 Why are we going DIGITAL?

17 Binary Signals Defined as being: ON or OFF High or Low 1 or 0

18 Simple Digital Signals

19 Simple Digital Signals Letter a Morse Code 1 Digital Binary

20 What s a digital signal?.

21 Analogue Signals analogue - signal can vary smoothly between maximum and minimum values

22 What happens to our signal?

23 Analogue transmission original signal attenuated signal - noisy and diminished

24 Analogue transmission amplification restores level but Also amplifies noise

25 Digital transmission original signal attenuated digital signal

26 Digital transmission restored digital signal ( regenerated signal)

27 What are their uses? Analogue signals e.g. radio, t.v. This is a way of carrying information using radiowaves The radiowaves vary in amplitude and frequency Digital signals e.g. computers, digital t.v. This is a way of carrying information using light or infrared radiation that is switched on and off in a series of pulses

28 Which is best? Analogue waves are easily produced and our sense organs/brain understand them. Digital waves are needed for computers to work. They can carry more information than analogue waves because digital pulses can be made very short, so you can send a lot of them. They are less easily degraded so the signal quality is higher.

29 Analogue Signals Sent as a wave which changes in frequency or amplitude to send the signal Digital Signals Sent as a series of pulses using a code. This code is called binary and is made up from 1s and 0s Amplitude Frequency Changes (AM) Changes (FM) Sent as radio waves, microwaves or down electrical wires Sent as pulses in optical fibres or electrical wires Signals suffer from noise which gets worse every time it is amplified Signals suffer from noise but it is easy to get the signal back Can t carry much information Can carry lots of information

30 Digital communication system Rapid transmission

31 Multiplexing -technique for increasing transmission rate -interweave the 2 (or more) signals 31