5.1 - Basic Waves Flashcards
What does a wave do
A wave is a means for transferring energy via oscillations
Whilst energy moves from one place to another, the waves cause no net movement of any matter
What’s a mechanical wave
It’s a wave in which there needs to be some sort of material medium - a substance that oscillates to allow the transfer of energy
What’s an electromagnetic wave
They can transfer energy through repeated oscillations of electric and magnetic fields, but these fields do not need matter to support them (unlike a mechanical wave)
The interaction between em wave and matter generally slows their transfer or energy - eg light travels more slowly in water than it does in a vacuum
Tell me the 2 ways of graphing waves
Displacement (y) and distance travelled (x)
Or
Displacement (y) and time (x)
Both look like a transverse wave going up and down
What does the displacement distance show
Shows the Physiical scale of the oscillations and the movement of energy
What does the displacement time graph show
It shows how the wave vibrations occur over time
Define wave displacement
The position of a particular point on a wave, at a particular instant in time, measured from the mean (equilibrium) position
Symbol is usually x, measured in metres
What’s the wave amplitude
The magnitude of the maximum displacement reached by an oscillation in the wave
Symbol = A and measured in metres
Define wave frequency
The number of complete wave cycles per second
This may sometimes be measured as the number of complete waves passing a point per second
Symbol = f and units hertz
Define wavelength
The distance between a point on a wave and the same point on the next cycle of the wave
Eg peak to peak
Symbol = lander thing, units in metres
Define the wave period
It’s the time taken for one complete oscillations at one point on the wave, this will also be the time taken for the wave to travel one wavelength
Symbol = T measured in seconds
Define the wave phase
The stage a given point on a wave is through a complete cycle
Phase is measured in angle units, as a complete wave cycle is considered to be the same as traveling around a complete circle, that is 360 degreee or 2 pi radians
No standard symbol, measured in SI units rad
Define the wave speed
The rate of movement of the wave - the same as speed in general
Symbol v or c for em waves and units m per second
What’s the wave equation
Wave speed = frequency x wavelength
v = f x lander
How can we investigate the speed of sound
We can use a twin beam oscilloscope to find the extra time a sound takes to travel a short extra distance - one beam trace shows a sound picked up by a microphone held 50cm roughly from the loud speaker
The other trace shows the same sound picked up by a second microphone held further from the loud speaker
The difference in positions of the peaks on oscilloscope shows the time taken for the sound to travel the extra distance this we can work out the speed v = d/t
Must synchronise the traces to minimis the effect of random error - make sure the traces are in phase and so that’s one wavelength so we can set frequency on signal generator and the. Use wave equation
Tell me about pulse echo measurements
Bats use echolocation using very high frequency sound pulses, gives a much more detailed perception of the world at distances less than 5m
- doesn’t work far away
A sound pulse is sent out and is reflected by objects and a bat can measured the time to instinctively calculate the distance to the reflecting objects using d = s x t
Tell me about human use of echo location
We have developed similar pulse echo ranging and imaging systems in a very wide range of technological applications from sonar on ships and submarines to air traffic control radar, medical imaging and the measurement of distance to asteroids and to the moon - it can avoid the need to land on the planet
How do humans use similar pulse-echo ranging and imaging systems in a range of technological applications
We use it for sonar on ships and submarine to air traffic control radar, medical imaging and the measurement of distance to asteroids and to the moon
Oh lol this is the same as another question but I already typed it now so hav 2
How can the time period / period of a wave be calculated
T = 1/ f
F = frequency
What’s a transverse wave
It’s one where the movements of the particles, or fields in an electromagnetic wave, are up and down or left and right whilst the energy travels forwards
What’s a longitudinal wave
In a fluid, eg air, the wave is generated by squashing particles together and then stretching them apart from eachother, repeatedly - thus vibrating them longitudinally
The areas of high pressure cause the particles to push apart from each other - making the particles move and squash their neighbours and so on - higher pressure is known as a compression
Where there are too few particles it’s a rarefaction
How can we illustrate / graph longitudinal waves
We have to turn the numbers into numbers so we can draw it on a displacement distance graph so it looks like a transverse wave so we can get amplitude and wavelength from the graph
What are sound waves caused by
Oscillations of particles of a medium, causing compressions and rarefactions along the line of movement of the wave
A compression occurs when particles either side are displaced towards it - displaced in opposite directions towards eachother
What does an oscilloscope show
The vibrations over time
Tell me about primary/ p waves
A type of seismic wave, faster than S waves
They are longitudinal as they push and pull as it travels
Tell me about secondary / s wsves
They are transverse and shake from side to side as waves travel
Define a transverse wave
It’s one in which the oscillations occur perpendicular to the direction of movement of wave energy
Define a longitudinal wave
It’s one in which the oscillations occur parallel to the direction of movement of wave energy
Define a compression
Is an area in a longitudinal wave in which the particle oscillations put them close to each other then their equilibrium state
Define a rarefaction
Is an area in a longitudinal wave in which the particle oscillations put them future apart from eachother than their equilibrium state
