3.1 waves introduction
TRANSCRIPT
Define a wave
Recall the major characteristics of a waveFrequency
Amplitude
Wavelength
Phase
Speed
Time
Distinguish between the properties of longitudinal and transverse waves
Distinguish between the properties of mechanical and electromagnetic waves
Determine the amplitude, wavelength and period of simple waveforms.
Waves are periodic oscillations that transfer energy from one point to another.
We generally think of this when we think of waves:
Mechanical Waves Involve the oscillations of matter to facilitate the
transfer of energy. Matter includes air, water, solids - anything! Wave motion is produced in two main ways:
Transverse – Wave oscillation is perpendicular to wave velocity direction
Longitudinal – Wave oscillation is in the same direction to wave velocity direction
Electromagnetic Waves Require no medium to travel, since they are oscillations
of the electromagnetic field. Always transverse waves
Mechanical Waves Strings, Ocean Waves, Sound, etc
The frequency of mechanical waves determines if we can hear them or not (audible spectrum).
In fluids (air and water), sound waves are almost exclusively longitudinal.
A vibrating guitar string is a transversewave
Sound travels from the guitar string to your ear in a longitudinal wave
Electromagnetic WavesLight, Radio Waves, X-rays, all oscillations
of the electromagnetic field.
The frequency of electromagnetic waves determines if we can see them or not. (visible spectrum)
You will learn more about light waves in particular in year 12
Transverse VS Longitudinal
http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html
TRANSVERSE: Particles oscillate perpendicular to wave motion (up and down):
LONGITUDINAL: Particles oscillate parallel to wave motion (back and forth)
Fill in the blanks: Listening to mad tunes on Triple J:
Sick Tunes
Radio Station
Radio
Listener
Mechanical/ElectromagneticLongitudinal/Transverse
Mechanical/ElectromagneticLongitudinal/Transverse
Mechanical/ElectromagneticLongitudinal/Transverse
Fill in the blanks: Listening to mad tunes on Triple J:
Sick Tunes
Radio Station
Radio
Listener
MechanicalLongitudinal
ElectromagneticTransverse
MechanicalLongitudinal
Term Definition SI units
Frequency ( f ) Number of fluctuations/ oscillations/cycles per second
Hz or s-1
Wavelength ( λ ) The distance between each successive wave
m
Period ( T ) The time between each successive wave
s
Speed ( v ) The velocity of the wave ms-1
Phase ( ϕ ) A particular point in the wave cycle (useful for comparing waves)
It’s complicated (it’s usually an angle, but let’s not get into it!)
Amplitude ( A ) The deviation from the mean, of whatever is being studied. (e.g. displacement, pressure, etc)
Whatever the units of what is changing over time (e.g. m, Pa, etc)
Representing Waves Waves can be represented typically in one of Two
ways
Amplitude VS Time (Temporal)
Visualising the Period of the Wave
Amplitude VS Distance (Spatial)
Visualising the Wavelength of the Wave
Ocean wave as measured by eye
This is a measurement of Amplitude VS Distance
wavelength
Amplitude
DISTANCE
Crest
Trough
Ocean wave as measured by a pressure sensor over time
This is a measurement of Amplitude VS Time
Period
AmplitudeTIME
Crest
Trough
Importantly Both Transverse and Longitudinal waves are
represented the same way on a graph.
Heinneman Physics 3A/3B – pg 189
Your Turn
What is the amplitude and wavelength of this wave?
Your Turn
What is the amplitude and wavelength of this wave?
Amplitude = 4 cmWavelength = 20 cm
λ
A
Your Turn
What is the amplitude and period of this wave?
Your Turn
What is the amplitude and period of this wave?
Amplitude = 90 mmWavelength = 50 y
T
A
How did you go?Define a waveRecall the major characteristics of a wave
Frequency AmplitudeWavelength Phase Speed Time
Distinguish between the properties of longitudinal and transverse waves
Distinguish between the properties of mechanical and electromagnetic waves
Determine the amplitude, wavelength and period of simple waveforms.