Waves Flashcards
How is a wave produced?
A wave is produced by a disturbance/ vibration/oscillation which transfers energy and information.
wavelength (lambda) (m)
The distance between any 2 consecutive waves (eg: 2 consecutive crests or troughs)
Transverse
It is produced when the disturbance/ vibration is perpendicular (90 degrees) to the direction of energy transfer.
examples of transverse waves
Electromagetic waves, S-waves secondary seismic waves (earthquakes), ripples on the surface of water, electromagnetic waves (such as radio, light, X-rays etc).
longitudinal wave
It is produced when the disturbance/ vibration is parallel to the direction of energy/ data transfer
Examples of longitudinal waves
(P) Primary seismic waves, SOUND waves, pressuure waves caused by repeated movements in a liquid or gas
ampLitude (A)
The distance from the rest/ median/ equilibrium/ 0 line to the crest or trough. unit= metres
What does ampLitude indicate?
Loudness
FrequenCy
It is the number of complete waves that pass a point in a second (unit -Hertz, Hz).
What does frequenCy determine?
The pitch
Period
It is the time taken for one complete wave to pass a point (unit- second)
Wavespeed (v)
frequency (Hz) x wavelength (m). It is the product of frequency (Hz) and wavelength (m)
Frequency =
1/time period (s)
EleCtromAgneTic waves
An electromagnetic wave is generated or produced when a Charged particle Accelerates. When a charged particle accelerates, the electric field and magnetic field change.
Electromagnetic spectrum (Real Men In Love Usually C-ray Girls)
Radio Micro Infrared Visible light Ultraviolet X-ray gamma ray
As you go down the electromagnetic spectrum, what happens to wavelength and frequency?
The wavelength decreases and the frequency increases.
Describe the electromagneTic spectrum
Electromagnetic radiation travel as transverse waves and transfers energy from one place to another. All electromagnetic waves can travel through a vacuum- the speed of light. The electromagnetic spectrum is a continuous range of wavelengths. The types of radiation that occur in each part of the spectrum have different uses and danger which depend on their wavelengths and frequency.
Properties of electromagnetic waves
- They are transverse in nature
- They can be reflected and refracted
- They all travel at the same speed in a vacuum (3x 10^8)
- They transfer energy
- Polarisation (cuts out the glare)
Sound waves
They are longitudinal. They travel as vibrations. They are made up of compressions and rarefactions and are detected by our ear drums. These vibrations are converted to electrical signals in the cochela. Sound can travel through solids, liquids and gases but they cannot travel through vacuums. This is because a vacuum has no particles to vibrate.
Properties of transverse waves:
- the energy transfer is in the same direction as the wave motion
- They transfer energy, but not the particles of the medium
- Transverse waves can move in a liquid or solid, but not a gas
- Some transverse waves (electromagnetic waves) can move in a vacuum.
The point on the wave that is highest above the rest position is called the
peak or crest
The lowest below the rest position is called what?
the trough
What are waves?
Repeated vibrations that transfer energy. Energy is transferred by parts of the wave knocking nearby parts.
Representing transverse waves
- They are drawn as a single, continuous line, usually with a central line showing the undisturbed position
- The curves are drawn so that they are perpendicular to the direction of energy transfer
Properties of longitudinal waves
- The energy transfer is in the same direction as the wave motion
- they transfer energy but not the particles of the medium
- they can move in solids, liquids and gases
- They can not move in a vacuum (since there are no particles).
The key features of a longitudinal wave are where the points are
- close together, called compressions
- spaced apart, called rarefactions
What type of waves can be seen in a slinky spring?
Longitudinal waves when it is moved quickly backwards and forwards.
Representing longitudinal waves
- they are usually drawn as several lines to show that the wave is moving parallel to the direction of energy transfer
- drawing the lines closer together represents the compressions
- drawing the lines further apart represents the rarefactions
How can transverse waves be shown on ropes?
The waves travel perpendicular to the vibration of the rope
How can longitudinal waves be shown in the vibration of coils?
The waves travel parallel to the vibration of coils.
Transverse waves vs Longitudinal waves
- structure: Transverse- peaks and troughs, longitudinal- compressions and rarefactions
- vibration: transverse-90 degrees to direction of energy transfer. Parallel to direction of energy transfer.
- vacuum: transverse- only electromagnetic waves can travel in vacuum, longitudinal waves cannot travel in a vacuum
- Material: tranverse waves- can move in liquids and solids, but not gases. Longitudinal waves- can move in gas, liquids and solids
- density: transverse waves- constant density, longitudinal waves- changes in pressure
- speed of wave: transverse waves- dependant on material it is travelling in, longitudinal waves: dependant on material it is travelling in.
wavefronts
- both transverse and longitudinal waves can be represented as wavefronts: this is where the waves are viewed from above
- For a transverse wave: one line represents either a peak or a trough.
- For a longitudinal wave: one line represents either a compression or a rarefaction
- The arrow shows the direction the wave is moving and is sometimes called a ray
- The space between the lines represents the wavelength : - when the lines are close together , this is a wave with a short wavelength.When the lines are far apart, this is a wave with a long wavelength.
Q: How does a toy duck demonstrate that waves do not transfer matter
- The type of wave on the surface of a body of water is a transverse wave
- This is because the duck is moving perpendicular to the direction of the wave
- The plastic duck moves up and down but does not travel with the wave
- both transverse and longitudinal waves transfer energy, but not the particles of the medium
- 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
- Objects floating on the water simply bob up and down when waves pass under them, demonstrating that there is no movement of matter in the direction of the wave, only energy.
In a transverse wave, the wavelength can be measured from
one peak to the next peak
In a longitudinal wave, the wavelength can be measured from
the centre of one compression to the centre of the next
The distance along a wave is typically put on the
x-axis of a wave diagram
Wavespeed definition
The distance travelled by a wave each second
Measuring the speed of waves- measuring sound between two points
1, Two people stand a distance of around 100m apart
2, The distance between them is measured using a trundle wheel
3, One person has two wooden blocks, which they bang together above their head
4, The second person has a stopwatch which they start when they see the first person banging the blocks together and stops when they hear the sound
5, This is then repeated several times and an average value is taken for the time
6, The speed of sound can be calculated using the equation: speed of sound = distance travelled by sound/time taken.
measuring the speed of waves - using echoes
1, A person stands 50 m away from a wall (or cliff) using a trundle wheel to measure this distance
2, The person claps two wooden blocks together and listens for the echo
3, The person then starts to clap the blocks together repeatedly, in rhythm with the echoes
4, A second person has a stopwatch and starts timing when they hear one of the claps and stops timing 20 claps later
5, The process if then repeated and an average time calculated
6, The distance travelled by the sound between each clap and echo will be (2x50 m)
7, The total distance travelled by sound during the 20 claps will be (20 x 2 x 50) m
8, The speed of sound can be calculated from this distance and time using the equation:
speed of sound = ( 2 x distance to the wall)/ time taken
Measuring the speed of waves- using an oscilloscope
1, Two microphones are connected to an oscilloscope and placed about 5m apart using a tape measure to measure the distance
2, The oscilliscope is set up so that it triggers when the first microphone detects a sound, and the time base id adjusted so that the sound arriving at both microphones can be seen on the screen
3, Two wooden blocks are used to make a large clap next to the first microphone
4, The oscilliscope is then used to determine
How do you visualise a transverse wave?- slinky
One student holds the end of the slinky stationary. The other end of the slinky is moved from side to side. A series of pulses moves down the slinky, sending energy from one end to another. The student holding the slinky still feels the energy as it arrives. None of the material in the slinky has moved permanently. The transverse waves transfer energy along the slinky from one end to the other.
Water waves and light waves are two examples of
transverse wave
Water wave
Energy is carried outwards by the wave, but water does not pile up at the edge of the pond.