Physics - P1.5 - Waves - Revision Cards in GCSE Physics

P1.5.1 - The Nature of Waves

Waves - used to transfer energy and information, direction of travel = direction wave transfers energy
Different types of waves:
- transverse wave - oscillation of particles is perpendicular to direction wave travels
- longitutinal wave - oscillation of particles is parallel to waves travel direction, made up of compressions and rarefactions
- electromagnetic waves - light and radio waves, travel through vacuum, no particles - waves are oscillations in electric and magnetic fields, oscillation is perpendicular to direction wave travels - tranverse waves
- mechanical waves - waves on springs, and sound waves, travel through a medium - transverse or longitudinal
Sound waves are longitudinal waves

1 of 7

Amplitude - height of wave crest, or depth of wave trough, from rest position, greater amplitude = more energy carried
Wavelength - transverse: distance from one crest, or trough, to the next, longitutinal: middle of one compression, or rarefaction, to the middle of the next
Frequency - transverse: number of wave crests passing a point in one second, longitudinal: number of compressions passing a point in one second, unit - hertz (Hz) - equivilant to per second (s)
Speed of wave - v = f x λ
- v - wave speed - m/s
- f - frequency - Hz
- λ - wavelength - m

2 of 7

Image seen in a mirror is due to reflection of light
Incidence ray - goes towards the mirror
Reflected ray - goes away from mirror
Normal - perpendicular to mirror, at the point incidence ray hits mirror
Angle of incidence - angle between incidence ray and normal
Angle of reflection - angle between reflected ray and normal
Any reflected ray - angle of incidence = angle of reflection
Image in a plane mirror is: same size, upright, same distance behind mirror, virtual
Real image - can be formed on a screen - rays of light that produce image actually pass through it
Virtual image - can't be formed on a screen - rays of light that produce image only appear to pass through it

3 of 7

Waves change speed and wavelength when cross a boundary between different substances, frequency stays the same
Refraction - property of all waves, including light and sound
Change in speed of the waves causes change in direction
Light enters more dense substance - slows down, changes direction towards normal
Light enters less dense substance - speeds up, changes direction away from normal
If wave is travelling along normal it won't change direction
Different colours of light - different wavelength and refracted by slightly different amounts - when white light is shone onto a triangular prism, spectrum is produced - dispersion
Violet light refracted most, red light refracted least

4 of 7

Diffraction - property of all waves, including light and sound - spreading of waves when passing through a gap or around an obstacle
Effect is most noticable if wavelength of wave = size of gap or obstacle
TV signals carried by radio waves - people living in hilly areas may not receive signal as a hill is blocking it - radio waves passing the hill will be diffracted around the hill - don't diffract enough = poor radio or TV signal

5 of 7

Casued by mechanical vibrations
Travels as a wave through solids, liquids and gases - fastest in solids and lowest in gases - can't travel through a vacuum
Longitudinal waves, direction of vibration = direction of travel
Range of frequences heard by humans - 20-20000Hz - decreases with age
Reflected to produce echoes - only hard, flat surfaces reflect sound, soft things absorb sound, an empty room will sound different once things are put in it
Refraction takes place at boundaries between layers of air at different temperatures
Sound waves can also be diffracted

6 of 7

Pitch depends on frequency of sound waves - higher frequency = higher pitch
Loudness depends on amplitude of sound waves - greater amplitude = more energy carried by wave = louder sound
Differences in waveform can be shown on an oscilloscope
Tunng forks and signal generators produce 'pure' waveforms - quality of note depends on waveform
Different instruments = different waveforms - sound different
Vibrations created in an instrument when it's played produce sound waves
In some instruments, a column of air vibrates, others, a string vibrates, some instruments vibrate when struck

7 of 7