Topic 4- Waves Flashcards
How do waves transfer energy
From one place to another without transferring any matter
What happens when waves travel through a medium
The particles of the medium vibrate and transfer energy and information between each other. But overall particularly stay in the same place
What is the amplitude of a wave
The displacement from the rest position to crest or trough
What is wave length
Is the length of a full cycle of the wave
E.g. from crest to crest or from compression to compression
What is the frequency of a wave
The number of complete cycles of the wave passing a certain point per second
How is frequency measured
In hertz
What is the period of a wave
The number of seconds it takes for 1 full cycle
How do you work out period
Period = 1/frequency
What ways are the vibrations of transverse waves
Sideways, vibrations are perpendicular (90 degrees)to the direction the wave travels
Examples of transverse waves
All electromagnetic waves
S-waves
Ripples and waves in water
What direction are the vibrations of longitudinal waves
Vibrations are Parallel to the direction the waves travel
What are example of longitudinal waves
Sound waves
P-waves
What do longitudinal waves do to the arrangement of particles
They squash up and stretch out the arrangement of particles in the medium they pass through making compressions (high pressure, lots of particles) and rarefactions (low pressure, fewer particles)
How do you work out wave speed
Wave speed = distance/ time
V=x/t
Wave speed = frequency x wavelength
V=f λ
How do you measure the speed of sound
Using an oscilloscope
What do you add to a speaker so you can generate sound with a specific frequency
By attaching a signal generator to a speaker so you can generate sound with a specific frequency
What do you use to find the wavelength of sound waves generated
Two microphones and an oscilloscope
How does a oscilloscope measure the speed of sound
Attach a signal generator to a speaker so you can generate sounds with a specific frequency.
Use two microphones and an oscilloscope to find the wavelength of the sound waves generated
- Set up the oscilloscope so that the detected waves at each microphone are shown as separate waves
- Start with both microphones next to the speaker, then slowly move one away so the two signals are aligned on the display, but have moved exactly one wavelength apart
- Measure the distance between the microphones to find one wavelength
- Use the formula v=f λ to find the speed of the sound waves passing through the air - the frequency is whatever you set the signal generator to in the first place
How do you measure the speed of water ripples using a strobe light
- Using a signal generator attached to the dipper of a ripple tank you can create water waves at a set frequency
- Dim the light and turn on the strobe lights - you’ll see a wave pattern made by the shadows of the wave crests on the screen below the tank
- Alter the frequency of the strobe light until the wave pattern on the screen appears to ‘freeze’ and stop moving. This happens when the frequency of the waves and the strobe light are equal - the waves appear not to move because they are being lit at the same point in their cycle each time .
- The distance between each shadow line is equal to one wavelength. Measure the distance between lines that are 10 wavelength apart, then find the average wavelength
- Use v=f λ to calculate the speed of the waves
How do you find the speed of waves in solids
By measuring the frequency of the sound waves produced when you hit the object
E.g. a rod with a hammer - the rod causes waves to be produced along the rod
