Electromagnetic EM Spectrum The Electromagnetic Spectrum Light a

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Electromagnetic (EM) Spectrum

Electromagnetic (EM) Spectrum

The Electromagnetic Spectrum ? Light, a type of radiation, is part of the electromagnetic

The Electromagnetic Spectrum ? Light, a type of radiation, is part of the electromagnetic spectrum. ? The electromagnetic spectrum is made up of different types of radiation. ? The different types of radiation have different properties and behaviour. TRUE/FALSE ? All electromagnetic waves can travel through space. TRUE/FALSE ? All electromagnetic waves travel at the same speed [300, 000 m/s in a vacuum]. TRUE/FALSE

Dispersion of white light

Dispersion of white light

Colour, wavelength and amplitude We can see the relationship between colour, wavelength and amplitude

Colour, wavelength and amplitude We can see the relationship between colour, wavelength and amplitude using this animation F

Electromagnetic Spectrum Although all EM waves travel at the same speed, their wavelength [

Electromagnetic Spectrum Although all EM waves travel at the same speed, their wavelength [ ] and frequency [ƒ] can be different. Waves that cook food. Waves that cause sun -tans. The properties, dangers and uses of EM waves depends on the wavelength [ ].

TRANSVERSE WAVES EM waves are transverse waves http: //www. walterfendt. de/ph 14 e/emwave. htm

TRANSVERSE WAVES EM waves are transverse waves http: //www. walterfendt. de/ph 14 e/emwave. htm

TRANSVERSE WAVES Electrical/Magnetic field The electric and magnetic fields vibrate at right angles to

TRANSVERSE WAVES Electrical/Magnetic field The electric and magnetic fields vibrate at right angles to the direction of movement of the energy Energy Movement

Electromagnetic Spectrum Wavelength ( ) increases Radio Micro Infra. Red Light Ultra. Violet X

Electromagnetic Spectrum Wavelength ( ) increases Radio Micro Infra. Red Light Ultra. Violet X rays Gamma Gate X of a phrase Usually Lets help you In remember Can you think that would Low Most frequency this Radiation order? Low frequency High frequency Long wavelength Short wavelength High energy Low energy High energy Most penetrating Leastpenetrating Most Low energy Least penetrating

Uses and dangers of EM radiation Need to know the uses and dangers of

Uses and dangers of EM radiation Need to know the uses and dangers of the various radiations: Radiation Gamma X-rays Ultraviolet Light Infra red Microwaves Radio waves Uses Dangers

EM Radiation: Gamma Uses: Kills harmful bacteria in food, sterilising surgical equipment, killing cancer

EM Radiation: Gamma Uses: Kills harmful bacteria in food, sterilising surgical equipment, killing cancer cells, gamma camera. Dangers: High doses can kill cells, lower doses can cause cells to become cancerous.

EM Radiation: X rays Uses: Shadow pictures of luggage and inside the human body.

EM Radiation: X rays Uses: Shadow pictures of luggage and inside the human body. Dangers: High doses can kill cells, lower doses can cause cells to become cancerous. How Hospital do hospital workers limit exposure their to exposure Gamma to and Gamma X rays and by standing X rays? behind lead shields or by leaving the room when the radiations are being used.

X rays How are X rays slides formed? q X rays can penetrate soft

X rays How are X rays slides formed? q X rays can penetrate soft tissue but not one b_____. X rays are bsorbed more by a_______ some materials than hotographic others. P____ f____ ilm is used to detect X rays. What colour does the photographic film go when it is hit by X-rays? black

EM Radiation: Ultraviolet Uses: Sun beds, fluorescent lamps and security marking. Dangers: The higher

EM Radiation: Ultraviolet Uses: Sun beds, fluorescent lamps and security marking. Dangers: The higher the frequency Which type of radiation of the radiation, the more is the most dangerous? dangerous it is. So gamma is more dangerous than X rays or ultraviolet. High doses can kill cells, lower doses can cause cells to become cancerous.

EM Radiation: Light Uses: Seeing and endoscopes. Dangers: Blindness

EM Radiation: Light Uses: Seeing and endoscopes. Dangers: Blindness

EM Radiation: Infrared Uses: Remote controls (TV/VCR), radiant heaters, grills, optical fibre communication, night

EM Radiation: Infrared Uses: Remote controls (TV/VCR), radiant heaters, grills, optical fibre communication, night vision. Dangers: Skin burns

Night vision Light is hot. All objects above absolute zero emit infrared radiation. The

Night vision Light is hot. All objects above absolute zero emit infrared radiation. The hotter an Which aremore the heat object is, the hottest/coolest parts radiation it emits. Some of the image shown? animals and cameras can detect infrared radiation and are able to build up a heat picture. Dark is cold.

EM Radiation: Microwaves Uses: Satellite communication, mobile phone networks, cooking. Dangers: Internal tissue heating.

EM Radiation: Microwaves Uses: Satellite communication, mobile phone networks, cooking. Dangers: Internal tissue heating.

Microwaves How do microwaves cook foods? Microwaves can be used in c_____ ooking because

Microwaves How do microwaves cook foods? Microwaves can be used in c_____ ooking because many foods contain w____ ater molecules. Microwaves of the right w____ avelength are able to make the water molecules v_______. ibrate This causes the food to get h____. otter

EM Radiation: Radio waves Uses: Communication and astronomy Dangers:

EM Radiation: Radio waves Uses: Communication and astronomy Dangers:

Radio waves The longer wavelength radio waves from a transmitter reflect off the Earth’s

Radio waves The longer wavelength radio waves from a transmitter reflect off the Earth’s outer atmosphere (ionosphere). How do radio signals from the UK reach around the globe?

Getting hotter If electromagnetic radiation is incident upon a An alternating current could be

Getting hotter If electromagnetic radiation is incident upon a An alternating current could be induced in the material, temperature of the material could increase. with. The the same frequency as the incident radiation. material what effects could it have? 21º C 30º 50º 70º

EM Questions 1) Match up the following parts of the electromagnetic spectrum with their

EM Questions 1) Match up the following parts of the electromagnetic spectrum with their uses : Gamma rays Allow us to see Radio waves Remote Controls Ultra Violet ‘See’ broken bones Visible Carry TV signals Microwaves Satellites X rays Sterilise equipment Infra Red Causes sun-tans

EM Questions 2) Which radiations are missing from below? Gamma A Ultraviolet Light Infrared

EM Questions 2) Which radiations are missing from below? Gamma A Ultraviolet Light Infrared A. ______ X rays B. ______ Microwaves B Radio waves

The wave equation c = 300, 000 m/s Speed of light/c (m/s) Frequency/f wavelength/

The wave equation c = 300, 000 m/s Speed of light/c (m/s) Frequency/f wavelength/ (Hz) (m)

Wave equation questions • Q 1) what is the frequency of microwaves with a

Wave equation questions • Q 1) what is the frequency of microwaves with a wavelength of 20 cm? • Frequency = speed/wavelength » = 300, 000/0. 2 » = 1500, 000 hertz • Q 2) What is the wavelength of radio waves with a frequency of 16 MHz? • Wavelength = speed/frequency » = 300, 000/16, 000 » =18. 8 m

Total Internal Reflection Optical Whatfibres, are thethat are used in communication, applications of total

Total Internal Reflection Optical Whatfibres, are thethat are used in communication, applications of total use total internal reflection? You couldofbe asked A beam light to drawthe on the enters optical path of the beam fibre…. in an exam. …NOTE how it is refracted as it enters the fibre… …it travels down the fibre through repeated total internal reflections.

Digital and analogue What is the difference between a digital signal and an analogue

Digital and analogue What is the difference between a digital signal and an analogue signal? What could they look like graphically? Digital signals can only be in one of two states, e. g. 0 or 1. Analogue signals are a continuously changing variable.

Digital compared to Analogue ADVANTAGES DISADVANTAGES Signals are clearer because noise (interference) can be

Digital compared to Analogue ADVANTAGES DISADVANTAGES Signals are clearer because noise (interference) can be removed Digital hardware is expensive at the moment. Carry much more information. Digital hardware is much smaller. Easier to send digital over long distances because signal doesn’t weaken as fast. Although digital signals are unaffected by electrical interference, they don’t give a complete signal [just lots of samples] - some people feel that analogue vinyl records sound better than digital CDs for this reason. Electrical storms and Which Noise. Analogue issignal any carries unwanted is most Which signal Examples What Digital ofto isnoise? are? random thermal noise. prone information. noise? the most information?