AQA Physics A - Waves

condensed information about waves - chapter 12 of aqa physics A

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  • Created on: 02-04-10 20:02
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Waves & Vibrations.
In longitudinal waves, displacement of particles are parallel to the direction of travel. For example,
sound waves and waves in earthquakes.
In transverse waves, the displacement of particles are perpendicular to the direction of travel. For
example, light and water waves.
Plane polarisation occurs when all the vibrations in a wave are made to travel in a single plane. For
example a laser. Polarisation can be either vertical or horizontal.
Longitudinal waves already travel in one plane so they can not be polarised. Transverse waves can
oscillate in any plane so they can be polarised.
Measuring Waves

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Displacement is the distance and direction a particle moves from its equilibrium position.
Amplitude is the maximum displacement of a particle.
Wavelength is the distance between two adjacent vibrating particles.
Period is the time taken for one complete wave to pass a fixed point.
Frequency is the number of waves passing a given point every second.
The relationship between frequency and period is, time = 1/frequency.
The formula for the speed of a wave is, speed = frequency multiplied by wavelength.…read more

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Diffraction is the bending of a wave around an obstacle or through an opening. The smaller the gap
the greater the diffraction. The longer the wavelength the greater the diffraction.
Superposition.
The principle of superposition states that when two waves meet the sum of the individual
displacements will give the total displacement.
When a crest meets crest or a trough meets trough, a supercrest or a supertrough is formed as the
two waves reinforce each other creating a constructive interference.…read more

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Stationary & Progressive Waves.
Stationary waves are a result of a progressive wave travelling in one direction and its reflected wave
travelling in the opposite.
At fixed points along the wave they form points of zero displacement called nodes. At maximum
displacement the points are called antinodes. Adjacent nodes are always 180 out of step.…read more

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When the waves are in phase they reinforce each other and produce a larger wave. However if they
are out of phase then cancellation occurs.
The phase difference between two vibrating particles is zero if they are between adjacent nodes. If
the two particles are separated by an odd number of nodes then the phase difference is 180
Note that Stationary waves vibrate freely and do not transfer energy.
Staionary Progressive
Frequency.…read more

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Rachael

Thanks x

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