Electromagnetic spectrum

Learning today – copy • The main features and characteristics of

the Electromagnetic spectrum• The uses and dangers of EM spectrum

Electromagnetic spectrum Mini-book – Due 17th 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?)-

The EM spectrum is a continuous spectrum

Visible light

Visible light

λ ≈ 700 nm λ ≈ 420 nm

Ultraviolet waves

λ ≈ 700 - 420 nm

Ultraviolet waves

λ ≈ 700 - 420 nm λ ≈ 10 – 100 nm

X-rays

λ ≈ 700 - 420 nm

λ ≈ 10 – 100 nm

X-rays

λ ≈ 700 - 420 nm

λ ≈ 10 – 100 nm

λ ≈ 1 – 0.01 nm

Gamma rays

λ ≈ 700 - 420 nm

λ ≈ 10 – 100 nm

λ ≈ 1 – 0.01 nm

Gamma rays

λ ≈ 700 - 420 nm

λ ≈ 10 – 100 nm

λ ≈ 1 – 0.01 nmλ ≈ 0.001 – 0.00001 nm

Infrared waves

λ ≈ 700 - 420 nm

λ ≈ 10 – 100 nm

λ ≈ 1 – 0.01 nm

λ ≈ 0.001 – 0.00001 nm

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

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

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

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

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 - 103 m

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 - 103 m

Electromagnetic spectrum

Long Wavelength

Short Wavelength

Electromagnetic spectrum

Long Wavelength

Short Wavelength

Low Frequency

High Frequency

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 - 103 m

What do they all have in common? copy please

• They can travel in a vacuum• They travel at 3 x 108m.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)

What else do you need to know?

Electromagnetic spectrum

Long Wavelength

Short Wavelength

Low Frequency

High Frequency

Uses of microwaves

• Satellite TV and cellular phones

Uses of Infrared waves

• Remote controls for TVs and intruder alarms

Uses of X-rays

• Medicine and security

Dangers of microwaves and X-rays

You need top know the speed of light (c)

• 300 000 000 m/s• 3 x 108 m/s

Mini-book

Mini-book

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

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 21st June.

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.

Learning today – copy • Analogue and digital signals • The uses and dangers of EM

spectrum

Examples of analogue and digital systems

ANALOGUE DIGITAL

Advantages of using digital signals- copy1. 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

2. Much more information can be sent. CopyDigital 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.CopyComputers are digital devices!