- Created by: scientist123
- Created on: 30-05-15 14:36
- 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
- Frequency is the number of waves to pass a point per unit time.
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- 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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- 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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- 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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- 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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- 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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- 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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- 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 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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