P6 - Waves Flashcards
Define transverse waves
The oscillations are perpendicular (at right angles) to the direction of energy transfer.
Define longitudinal waves
The oscillations are parallel to the direction of energy transfer.
Give 1 example of transverse waves
Ripples on the surface of water
Give 1 example of longitudinal waves
Sound waves travelling in air
Longitudinal waves show areas of:
Compression (particles close together) and
rare fraction (particles spaced out)
What is the difference between transverse and longitudinal waves in terms of medium?
All longitudinal waves require a medium to travel through (air, liquid, solid)
Not all transverse waves require a medium.
Describe evidence for Both ripples on a water surface and sound waves in air that it’s the wave that travels and not the water or air itself.
Using a slinky to show the wave and a red dot to show a single point (water molecule/ air particle etc).
When the wave travels through, the dot oscillates up and down/ side to side but it does not travel along the medium.
Define Amplitude of a wave
The maximum displacement of a point on a wave away from its undisturbed position.
Define wavelength of a wave
The distance from a point on one wave to the equivalent point on the adjacent wave.
Define frequency of a wave
The number of waves passing a point each second (Hz).
Define period of a wave
The time (s) for one wave to pass a point.
Define wave speed
The speed at which the wave moves through the medium (ie the speed at which energy is transferred)
Wave speed equation
Wave speed (m/s) = frequency (Hz) x wavelength (m)
[v = f x (lambda)]
Describe a method to measure the speed of sound waves in air
2 people separated by 500m.
Person A has cymbals, person B has a timer.
B starts timing when they see A clash cymbals together.
B stops timing when they hear the sound of cymbals clashing.
Calculate wave speed by dividing distance travelled by time taken.
Describe the problems with this method and solutions (speed of sound waves in air)
Every person has a different reaction time.
(Use large no. of observers with timers and discard anomalies to calculate a mean)
Time between seeing cymbals clash and hearing sound is very short.
(Increase distance between person A and B)
Describe what happens when a wave hits a boundary with a different material
The wave can be transmitted through the material.
The energy of the wave could be absorbed by the material and won’t pass through the material.
The wave could be reflected off the surface of the material.
The (..) = the (…)
The angle of reflection = the angle of incidence
Describe how the human ear converts wave disturbances between sound waves and vibrations
Sound waves in the air are funnelled into the ear where they hit the eardrum.
The sound waves cause the ear drum and inner ear to vibrate.
This causes the sensation of sound.
What is the range of normal human hearing
20Hz to 20,000Hz
Explain why the ear/eardrum only works over a limited frequency range
Frequencies outside of the range may not be able to cause the eardrum to vibrate.
Describe how frequency effects sound
High frequency = high pitch
Low frequency = low pitch
Describe how amplitude effects sound
Small amplitude = quiet sound
Large amplitude = loud sound
Describe what is meant by ultrasound
Sound waves with a frequency higher than the upper limit of human hearing.
Describe how ultrasound is used for medical and industrial imaging
Ultrasound waves are partially reflected when they meet a boundary between two different media.
The time taken for the reflections to reach a detector can be used to determine how far away a boundary is.
Describe what is meant by seismic waves (P waves)
P waves are longitudinal waves.
They can pass through solids and liquids.
They travel at different speeds through solids and liquids.
P waves travel faster than S waves
Describe what is meant by seismic waves (S waves)
S waves are transverse waves.
S waves can only travel through solids.
