Waves CGP topic 2
Waves transfer energy and information without transferring matter. We can demonstrate that with a
water wave that the water vibrates air oscillates by placing on object on top of the water.
In a transverse wave the vibration is 90* to the direction of energy transfer. à electromagnetic, seismic,
water
In a longitudinal wave the vibration is parallel to the direction of energy transfer. à sound, seismic
There are two types of wave graph – a displacement/position graph and a displacement/time graph
• Displacement/position graphs à peak to peak or trough
to trough is the wavelength
• Displacement/time graph à peak to peak or trough to
trough is time period
!
Frequency is the number of oscillations in one second (hertz) à f = "
!
Time period is the time it takes for a source to produce 1 complete oscillation àT = #
Vibration = frequency × wave length
V = speed of wave (m/s)
F = frequency of wave (Hz)
Λ = wavelength (m)
Rubber band
Suspend a metal rod horizontally using clamp stands
and rubber bands. Hit the metal rod and measure the
sound wave via the frequency analyser app
Clamp stand
Metal rod
Sound
Sound is created through vibrating objects and are transmitted Although sound travels faster through solids, I
through vibrating particles. Sound waves are longitudinal and could hear someone better through air (a gas)
travel faster through solids as there are more particles to than if there was a wall between us as the wall
vibrate off of. Nobody can hear sound in space as there is a will reflect some of the sound and it would
vacuum so no particles can vibrate. also absorb the sound.
The compression is a region of slightly high-pressure where the
air molecules are closer together than usual. A rarefaction is
the opposite.
The wavelength of sound wave is equal to the distance between the centres of two successive compressions
or rarefactions.
, Core Practical – Investigating Waves
Ultrasound
Humans can detect soundwaves between 20Hz and 20,000Hz. Sound made by waves higher than this
frequency are called ultrasound. Some animals, such as dolphins, can detect objects around them using
ultrasound waves; they are reflected off things around and the animals listen for the echoes.
Ultrasound scans
• A probe is placed on the mother’s stomach that emits pulses of ultrasound.
• Ultrasound waves are partially reflected at boundaries of different
mediums, e.g. air/skin/muscle/fat/bone. And so, an echo is received by the
probe.
• The longer the echo takes to return, the further away the object being
scanned
• The reflected ultrasound waves are used to form an image of the baby
Echolocation
Sonar equipment carried on ships or submarines use a
similar method to find the depth of the sea or to detect fish.
A loudspeaker on the ship emits a pulse of ultrasound which
spreads out through the water and some of it is reflected by
the seabed. A special microphone on the ship detects the
echo and the sonar equipment measures the time between
the sounds being sent out and the echo returning.
Waves transfer energy and information without transferring matter. We can demonstrate that with a
water wave that the water vibrates air oscillates by placing on object on top of the water.
In a transverse wave the vibration is 90* to the direction of energy transfer. à electromagnetic, seismic,
water
In a longitudinal wave the vibration is parallel to the direction of energy transfer. à sound, seismic
There are two types of wave graph – a displacement/position graph and a displacement/time graph
• Displacement/position graphs à peak to peak or trough
to trough is the wavelength
• Displacement/time graph à peak to peak or trough to
trough is time period
!
Frequency is the number of oscillations in one second (hertz) à f = "
!
Time period is the time it takes for a source to produce 1 complete oscillation àT = #
Vibration = frequency × wave length
V = speed of wave (m/s)
F = frequency of wave (Hz)
Λ = wavelength (m)
Rubber band
Suspend a metal rod horizontally using clamp stands
and rubber bands. Hit the metal rod and measure the
sound wave via the frequency analyser app
Clamp stand
Metal rod
Sound
Sound is created through vibrating objects and are transmitted Although sound travels faster through solids, I
through vibrating particles. Sound waves are longitudinal and could hear someone better through air (a gas)
travel faster through solids as there are more particles to than if there was a wall between us as the wall
vibrate off of. Nobody can hear sound in space as there is a will reflect some of the sound and it would
vacuum so no particles can vibrate. also absorb the sound.
The compression is a region of slightly high-pressure where the
air molecules are closer together than usual. A rarefaction is
the opposite.
The wavelength of sound wave is equal to the distance between the centres of two successive compressions
or rarefactions.
, Core Practical – Investigating Waves
Ultrasound
Humans can detect soundwaves between 20Hz and 20,000Hz. Sound made by waves higher than this
frequency are called ultrasound. Some animals, such as dolphins, can detect objects around them using
ultrasound waves; they are reflected off things around and the animals listen for the echoes.
Ultrasound scans
• A probe is placed on the mother’s stomach that emits pulses of ultrasound.
• Ultrasound waves are partially reflected at boundaries of different
mediums, e.g. air/skin/muscle/fat/bone. And so, an echo is received by the
probe.
• The longer the echo takes to return, the further away the object being
scanned
• The reflected ultrasound waves are used to form an image of the baby
Echolocation
Sonar equipment carried on ships or submarines use a
similar method to find the depth of the sea or to detect fish.
A loudspeaker on the ship emits a pulse of ultrasound which
spreads out through the water and some of it is reflected by
the seabed. A special microphone on the ship detects the
echo and the sonar equipment measures the time between
the sounds being sent out and the echo returning.
