Complete set of notes for each specification point (3.1 - 3.29) for Topic 3 (Waves) of the GCSE Physics Edexcel IGCSE Exam Board. Suitable for 2024 or 2025 exams. Written by a GCSE Student, using lots of resources to create accurate notes to aid exams. Includes paper 1 and paper 2 notes (paper 2 is...
3. WAVES
A – Units:
3.1 – use the following units: degree (°), hertz (Hz), metre (m), metre/second (m/s) and second (s)
B – Properties of waves:
3.2 – explain the difference between longitudinal and transverse waves
Transverse waves:
o The direction of motion (propagation) of the wave is perpendicular to
the source motion
o They have peaks and troughs
o Transverse waves can move in a liquid or solid, but not a gas
o Some transverse waves (electromagnetic waves) can move in a
vacuum
o Examples – Electromagnetic waves (such as radio, light, X-rays etc)
Longitudinal waves:
o The direction of motion (propagation) of the wave is parallel to the
source motion
o They can move in solids, liquids and gases
o They cannot move in a vacuum (since there are no particles)
o Wavelength = one compression to the next
o Examples – sound waves
3.3 – know the definitions of amplitude, wavefront, wave speed, frequency, wavelength, time period,
peak/crest and trough
o Amplitude – the distance from the equilibrium position (middle point) to the maximum displacement (top of a
wave or bottom of a wave) – measured in metres – symbol A
o Wavefront – the space between each wavefront represents the wavelength – close together means
short wavelength, far apart means long wavelength
o Wave speed – the speed at which the wave travels –
measured in metres per second – symbol V
o Frequency – the number of waves passing a point in a
second – measured in Hertz (Hz) – symbol f
o Wavelength – the distance from one point on the
wave to the same point on the next wave – measured
in metres – symbol λ
o Time period – the time taken for one complete wave
to pass a point – measured in seconds – symbol T
o Peak – the highest point above the rest position
o Trough – the lowest point below the rest position
o Rest position – the position of particles when they are not moving
3.4 – know that waves transfer energy and information without transferring matter
o Waves transfer energy and information.
o They do not transfer the particles of the medium.
o This means when a wave travels between two points, no matter actually travels with it, the points on the wave
just vibrate back and forth about fixed positions.
, 3. WAVES
3.5 – use the relationship between speed, frequency and wavelength of a wave
3.6 – use the relationship between frequency and time period
o Frequency (f) = 1 / time period (T)
3.7 – use the above relationships in different contexts including sound waves
and electromagnetic waves
3.8 – explain why there is a change in the observed frequency and wavelength of a wave when its source is
moving relative to an observer, and that this is known as the Doppler effect
o The apparent change in wavelength and frequency of a wave
emitted by a moving source
o If a wave source is moving towards observer A, there will be a
increase in the observed frequency and a decreased in the
wavelength of a wave. This is because the wavefronts either get bunched together or spaced apart
o As it moves away from observer B, the distance between each wave front increases (as the sources has moved a
little during the time for one cycle) observed frequency decreases and wavelength increases
3.9 – explain that all waves can be reflected and refracted
Reflection:
o All waves can be reflected when travelling from a low density medium (air) to one of much higher density (glass)
o Law of reflection: angle of incidence = angle of reflection
o Frequency, wavelength and speed are all unchanged
Refraction:
o All waves can be refracted when the speed of a wave change when it enters a new medium
o Waves enters denser medium – speed decreases and bends towards the normal
o Therefore, the angle of refraction is smaller than the angle of incidence
o Waves enters less dense medium – speed increases and bends away from the normal
o Frequency stays the same but the wavelength changes
C – Electromagnetic spectrum:
3.10 – know that light is a part of a continuous electromagnetic spectrum and that all waves part of it travel
at the same speed in free space
o They are all transverse + can all travel through a vacuum
o They all travel at the same speed in a free space (speed of light in space is 3 x 10 8 m/s)
o They can all be reflected, refracted or diffracted
3.11 – know the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing
frequency, including the colours of the visible spectrum
Radio waves Microwaves Infrared Visible Light Ultraviolet X-Rays Gamma Rays
RAGING MARTIANS INVADED VENUS USING X-RAY GUNS
Lower energy Long wavelength Short wavelength Higher energy
Long wavelength Short wavelength
Red Orange Yellow Green Blue Indigo Violet
Low frequency High frequency
Richard Of York Gave Battle In Vein
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