Progressive waves transfer energy, without any net transfer of matter.

When a wave oscillates it transmits energy from one place to another.

A wavelength is the distance between two points that are in phase, e.g 2 peaks or 2 troughs.

With time on the x axis, it changes to period between 2 points.

f=1/T (Hz)

Only waves of the same type can interfere with eachother

Wave speed

Frequency is the number of waves to pass a point per unit time.

v=f(lambda)

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Different vibrations

Waves can be transverse or longitudinal

For transverse- vibrations are perpendicular to the direction of travel of the wave energy e.g light energy

For longitudinal - vibrations are parallel to the direction of travel of the wave energy e.g sound waves.

Where particles are compressed theyre called compressions and when spread out theyre called rarefactions

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wave instensity

Wave intensity

Intensity is the amound of wave energy per unit are per unit time

I=P/A (wm^-2)

I=P/4pi^2 for radial point sources

I =1/d^2

Double the distance, intensity will fall to a quarter of initial value.

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intensity spectrum

Continuous spectrum contains all the wavelengths.

Area= total energy emitted by the source

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intensity and amplitude

Distance is twice the amplitude

Doubling the amplitude with same frequency, the distance doubles, average speed doubles.

Kinetic energy quadruples as its proportional to v^2 and intensity quadruples.

Intensity is proportional to energy and therefore intensity is proportional to amplitude^2.

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polarisation

Plane polarised: Vibrations are confined to one plane only.

Only transverse waves can be polarised

Light can be polarised, sound no, radiowaves yes

Unpolarised light has vibrations in all planes perpendicular to direction of travel

polaroids polarise light

If the angles of the polariser and analyser are parallel, then all the transmitted light will pass through.

If they're perpendicular to eachother, the analyser will absorb all the polarised light.

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polarisation pracital applications

Reflected light from non-metallic surfaces is partially polarised, polarised sunglasses reduce glare.

You can enhance reflection in photography by aligning the polaroid filter with the polarised light.

Radio waves and microwaves, antannae produce and receive plane polarised waves.

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Reflection

Wavefronts represent peaks.

Distance between wavefronts is lambda

Take average e.g 6 waves divided by 6

Wavefronts are perpendicular to incident ray.

Draw the normal, all angles measured from it.

Incident angle equal to reflected angle

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Refraction

Wave change in speed as it crosses from one medium to another.

Change in direction if there's an angle between incident wave and normal

Light will refract towards the normal line as it enters and wavefronts are closer since it slows down so wavelength decreases since frequency remains constant.

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Refraction types

Light refracts towards the normal and slows down

Mechanical waves(sound) if it travels into a more dense medium, it refracts away from normal and speeds up.

Water wave into shallower water refracts towards normal and slows down

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Diffraction

Diffraction is the spreading out of waves as they pass through a gap or around a corner.

When the gap = size of wavelength there's maximum diffraction.

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