AQA Physics A - Chapter 12 Waves Revision Notes


These are notes I made for revision of unit 2 physics aqa a.

Hope you find them useful...

i will also upload the chapter 13 - optics notes to finish the waves topics


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  • Created on: 31-03-11 11:16
Preview of AQA Physics A - Chapter 12 Waves Revision Notes

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Waves & Vibrations
WAVE is any oscillation where energy is transferred in the direction of the wave travel
without the large scale/long distance permanent displacement of matter.
When waves progress through a substance, the EM waves are vibrating electric and magnetic fields
particles of the substance vibrate in a certain way that progress through space without the need for a
which makes nearby particles vibrate in the same substance.
way, and so on.
e.g. sound waves, seismic waves, waves on a string, e.g. Infrared Radiation, Heat, Light, Ultraviolet
water waves Radiation, XRays
Waves in which the direction of vibration is Waves in which the direction of vibration of the
perpendicular to the direction in which the wave particles is parallel to (along) the direction in which
travels. the wave travels.
You get a series of compressions and rarefactions.
e.g. waves on a string, EM waves, secondary e.g. sound waves, primary seismic waves
Waves which travel through a substance (or through Wave pattern with nodes and antinodes formed when
space if electromagnetic). Energy is transferred two or more progressive waves of the same frequency
along the wave. and amplitude pass through each other. Energy is
not transferred along the wave.

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Page 2

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Transverse Wave: DisplacementDistance Graph
Key Terms:
Displacement: distance and direction from the equilibrium point
Amplitude: maximum displacement from equilibrium
Wavelength: distance between 2 adjacent particles which have the same phase
Frequency: number of oscillations per second by the source / number of waves passing a point
per second.…read more

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Phase Difference:
PHASE DIFFERENCE between two vibrating particles is the fraction of a cycle between
the vibrations of the two particles.
Phase Difference is measured either in degrees or radians, where
1 cycle = 360° = 2 radians
For two points at distance (d) apart along a wave of wavelength ( )
P hase Difference in radians = 2
The diagram below shows three successive snapshots of the
particles of a transverse wave progressing from left to right across
the diagram.…read more

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DisplacementDistance graphs:
A displacementdistance graph is also called a displacementposition graph. It shows
the displacement of the particles at various positions at a certain time.
Although it looks like a photograph of a transverse wave, it can be used to describe
BOTH a transverse and a longitudinal wave (Figures a. and b.…read more

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Fig c. Time series of DisplacementDistance graphs of a wave.
Using a series of displacementdistance graphs at various times, we can see the
motion of the wave (Figure c.)
By comparing the changes in these graphs, we can deduce the travelling speed and
direction of the wave, as well as the timevarying directions of the motion of the vibrating
DisplacementTime graphs:
Unlike a displacementposition graph, a displacementtime graph describes the
displacement of ONE particle at various times at a certain position.
Figure d.…read more

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Period (and hence, the frequency)
Direction of motion of the particle at various times
If we have a snapshot of the wave too, we can deduce the motion of the wave (i.e. its
travelling speed and direction)
POLARISATION is the restriction of transverse waves using a filter (mechanical/
electronic) so that they have different amplitudes in different planes.
Unpolarised: No restrictions on vibrations (normal behaviour)
Plane (Linear) Polarised: Vibrations limited to one plane.…read more

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Unpolarised Polarised
Plane of Polarisation: The plane in which the medium oscillates and the energy is
propagated. (For Electromagnetic waves it is defined as the plane in which the electric field
Polarisation can be used to distinguish between longitudinal and transverse waves since only
transverse waves show polarisation effects. (Longitudinal waves propagate parallel to the
direction of motion so if polarised, you will effectively block the wave).…read more

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The light from the Polaroid is plane polarised, so the transmitted intensity will be a
maximum when the analyser is parallel to the plane of polarisation.
Intensity will be zero when analyser is at right angles to polariser.
In a 360° rotation of the analyser the intensity will vary continuously and have TWO
If unpolarised light is used and the Polaroid rotated 360° there will be no change in intensity.…read more

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Polaroid Sunglasses: Only let light polarised in one direction and absorb the rest.
Intensity is reduced. Also, reflected light and sunlight scattered from particles in the
atmosphere is partially polarised. If the Polaroid in the sunglasses is in the correct
orientation it can absorb the reflected light and greatly reduce glare.
Stress Patterns: Certain materials (especially polymers) rotate
the plane of polarised light as it passes through them. The
amount of rotation depends upon the stress the material is
under.…read more

Page 10

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REFRACTION is the change of direction of a wave when it crosses a boundary
where its speed changes.
This change in velocity means that the wavelength of the wave must change, since
frequency is constant and v = f
DIFFRACTION is the spreading of waves on passing through a gap or near an edge.
Every point on the wave acts as an independent emitter.
Satellite TV dishes in Europe need to point South, since the
satellites orbit the Earth directly above the equator.…read more




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