few topics in physics revision notes

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  • Created on: 30-05-13 15:38
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waves transfer energy from a source to other places
waves are a regular pattern of disturbances
in a transverse wave the disturbance is a right angles to the direction of travel of the wave
in a longitudinal wave the disturbance is parallel to the direction of travel of the wave
the amplitude is the maximum disturbance from equilibrium
it is measured in meters
the wavelength is the distance between one point on a disturbance and the same point on the next one
e.g., from crest to crest, tough to tough
it is measured in tough
the frequency is the number of waves produced by the source in one second, or the number of waves
passing a point in one second
it is measured in hertz
all waves can be reflected
all waves can be refracted
all waves can be diffracted
diffraction is the bending of a wave into the region of shadow as it passes an obstacle
-the wavelength, frequency and speed of the wave do not change
-the longer the wavelength, the more the wave is diffracted
when drawing diagrams to show diffraction, we use waveforms, not rays
since light has a very small wavelength these is only a very small amount of diffraction
since sound has a longer wavelength these is a larger amount of diffraction so sound is bent round
Waves through gaps
gap large compared to wavelength and there is little diffraction
gap smaller and a little more diffraction
gap the same size and wavelength and the waves become curved
Waves past obstacles
obstacle large compared to wavelength and there is little diffraction
obstacle smaller and there is more diffraction

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the image produced in the mirror is virtual, it is formed where the rays appear to come from
it is also upright an laterally inverted (back to front)
the angle of incidence and the angle of refraction are the same
sound are produced by vibrations
they travel as longitudinal waves which means the direction of oscillation is parallel to the direction of
travel of the sound
sound cannot travel through a vacuum but light can
sounds can bounce or reflect off hard surfaces…read more

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Communication using radio waves and microwaves
radio waves are used to transmit radio and TV programmes
the type of wave used depends on the frequency and hence the wavelength of the wave
ground waves: low frequency, long wavelength waves diffract and so can travel long distances even
through the earth is curved
sky waves: higher frequency (3-30MHz) waves are reflected form the ionosphere which enables them to
travel long distances despite the earth's curvature
line of sight waves: 30-300MHz waves are very high frequency radio…read more

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In parallel circuits:
potential difference is the same across all components
total current is shared between branches
The current through a component depends on its resistance
Mains supply is AC
Battery supply is DC
Moving a magnet into a coil of wire induces a voltage
Transformers change AC voltage
Transformers work by electromagnetic induction
A current-carrying wire creates a magnetic field
A current is a magnetic field experiences a force
Fleming's left-hand rule tells you which way the force acts
Magnetic fields make current-carrying coils…read more


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