Waves Powerpoint Presentation

8/2/2019 Waves Powerpoint Presentation

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INVISIBLE WAVES

CARRIERS OF ENERGY


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SOUND WAVES1. When we speak, sound waves move outward

from us without any flow of air from one partof the medium to another.

2.The disturbances produced in the air canonly be detected by eardrums ormicrophones.

3.These patterns which can move without theactual physical transfer or flow of matter asa whole, are called waves.

4. In a wave, information and energy, in theform of signals propagate from one point to


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CONVERSATION


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Not all waves require amedium for

propagation

Light waves can travel throughvacuum.


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Central features of

Mechanical Waves1.They are governed by

Newtons Laws.2.They can exist only in

material medium, e.g.water, air and rock.


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Electromagnetic Waves

Visible light, ultraviolet

light, radio waves,microwaves and X rays

are common examplesof electromagneticwaves.


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Electromagnetic wavesAll types of electromagnetic waves travel atthe same speed through a vacuum (space).

The electromagnetic spectrum is continuousbut the wavelengths within it can be groupedinto types of increasing wavelength anddecreasing frequency:

gamma rays, X-rays, ultraviolet rays, visiblelight, infra red rays, microwaves and radiowaves.Different wavelengths ofelectromagnetic radiation are reflected,

absorbed or transmitted differently by


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Electromagnetic wavesWhen radiation is absorbed the energy it

carries makes the substance which absorbs ithotter and may create an alternating current

with the same frequency as the radiationitself.

Different wavelengths of electromagnetic

radiation have different effects on living cells.Some radiations mostly pass through softtissue without being absorbed, some produceheat, some may cause cancerous changesand some may kill cells. These effects dependon the type of radiation and the size of the


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The Electromagnetic

SpectrumLight forms a small part of a

large family ofelectromagnetic waves.You will know how light splits

into the colours of therainbow. The scientific termfor this is a spectrum.


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The rest of the electromagnetic spectrumis like this as well. Here is a picture that

sums up the electromagnetic spectrum (em-spectrum).


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WAVE FORMULAElectromagnetic waves obey the wave formula:

wave speed = frequency wavelength

(metre/second, m/s) (hertz, Hz) (metre,m)


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Electromagnetic waves are like waterwaves. They transfer energy from a sourceas waves. They have an electricalcomponent and a magnetic component, butyou don't need to know the details of them atthis stage.

All electromagnetic waves travel at the speedof light.

Speed of light (Physics code c) = 300 000

Features of

Electromagn

etic Waves


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WAVELENGTH


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DEFINING WAVELENGTH


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USES OF ELECTROMAGNETICWAVES

Radio waves, microwaves, infra red andvisible light can be used for communication.

Microwaves can pass through the Earthsatmosphere and are used to send information

to and from satellites and within mobile phonenetworks.

Infra red and visible light can be used to sendsignals along optical fibres and so travel in

curved paths.

Communication signals may be analogue(continuously varying) or digital (only on and

off). Digital signals are less prone tointerference than analogue and can be


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In the string, a compression and rarefactionmoves from one region to another, makingthe propagation of a disturbance possible inair.A compression increases the density by

packing the molecules together, which thentend to move out to the adjoining regioncreating a compression there and a rarefied

region is created in the previous area.


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The Transverse Wave


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Clickicontoaddpicture

Longitudinal Waves


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TRANSVERSE &LONGITUDINAL WAVES


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The Wave Equation

There are three measuredquantities in

electromagnetic waves:The speed;

The wavelength;

The frequency.


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wave speed (m/s) = frequency(Hz) wavelength (m)

v = f The strange looking symbol that

looks like an upside-down "y" islambda, a Greek letter "l". It isthe physics code for

wavelength. The other codes


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What is the frequency of Radio 4long wave that broadcasts at a

wavelength of 1500 m? c = f

We want the frequency so we must

rearrange:

f = c/

f= 3 108 m/s 1500 m = 200000 Hz = 200 kHz

H El t ti W


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How Electromagnetic WavesBehave

When an electromagneticwave (radiation) hits amaterial, it can be:

reflected, like light in amirror;absorbed, like heat absorbedby a black surface;transmitted, or passed on,

like light passing through


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GO TO FAVOURITES AND FIND USES OFELECTROMAGNETIC WAVES LIVE

1. Features of visible light waves.

2. Uses of gamma rays.

3. Uses of X-rays.

4. Uses of Ultraviolet rays.

5. Uses of Infra-red rays.6. Uses of Microwaves rays.

7. Uses of Radio waves.


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Features of visible light

waves.Light waves are a

series of changingmagnetic andelectric fields wherethe changes in a

magnetic field causea change in electricfield which causesanother electric field.

White light is amixture of all coloursof the visiblespectrum.

It consists of waves


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Uses of gamma rays.

Gamma Rays are veryhigh energy wavesreleased in bursts from thenucleus of certain atoms

like Uranium andPlutonium.

They are a form of nuclearenergy and are highly

radioactive.

Gamma rays are used todestroy cancer cells whichare more sensitive tothese rays than normal

f


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Uses of X rays.

X rays are produced when fast movingelectrons lose energy suddenly e.g whensmashing into a metal target.

Short wavelength X rays penetrate densemetals while long wavelength X rayspenetrate flesh but not bone.

It is used to photograph the inside of thebody.

ses o crowaves


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ses o crowaves.

Microwaves areshort wave radiowaves generatedby vibratingelectrons inelectrical devices.

They are easy todirect throughionosphere andhence are usedfor satellitecommunicationand mobilephones.

Food stronglyabsorbmicrowaves,


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Use of UltravioletwavesUV radiation receivedfrom the sun is a

good source ofvitamin D. However

too much exposurecauses damage tothe skin resulting insuntan to moresevere forms of skincancer.

UV is used to killbacteria.

Some washing


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raysThese rays have

frequency below red lightand give out heat.

They are released from

vibrating atoms ormolecules.

Hotter objects releasemore infrared rays.

Remote control devicesemit infrared rays whichare detected by special

components of TV. They


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Use of Radio Waves

Radio waves are generated by oscillatingelectrons e.g in a transmitting aerial.

Long radio waves are useful forcommunicating around the Earth as theydiffract along the Earths surface.Short radiowave stravel throughj ionosphere.

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Waves Powerpoint Presentation