Waves Water and Seismic Waves Transverse Waves Longitudinal Waves Frequency Period and Amplitude Crests Troughs and Wavelength Universal Wave Equation Waves Waves are disturbances which transfer energy over a distance ID: 795836
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Slide1
Waves – An Introduction
Waves
Water and Seismic Waves
Transverse Waves
Longitudinal Waves
Frequency, Period and Amplitude
Crests, Troughs and Wavelength
Universal Wave Equation
Slide2Waves
Waves are disturbances which transfer energy over a distanceThey all originate from vibrationsi.e. dropping a pebble into water
Examples: Water wavesWaves in a stringEarthquake waves
Slide3Waves
The vibrating source supplies energy which is transported along the medium as a waveThis vibration can be caused by many things from moving a string, rubbing objects together or having an object impact the ground or water
i.e. seismic waves are waves of energy created by earthquakes which travel through the earth and are caused by tectonic plates moving against each other
Slide4Waves
Waves pass their energy from one particle to another until it runs out of energy
Example: Water waves created from tectonic activity, volcanic eruptions, winds, impacts, etc. carry a lot of energy which can be used to inflict serious damage
Slide5VIDEO - TSUNAMI
Slide6Waves
We will be discussing two main types of waves
Transverse WavesLongitudinal Waves
Slide7Transverse Waves
The particles vibrate perpendicular to the direction of motion
Slide8Longitudinal WavesThe source vibrates parallel to the direction of motion
Slide9Transverse vs. Longitudinal Waves
Slide10Terminology
Regarding any kind of vibrating object:One complete oscillation is called a cycle
The number of cycles per second is the frequency (f)The unit for frequency is the hertz (Hz)The time required for one full cycle is the period (T)
The unit is usually the second but can be days, months, years, etc.
One complete cycle
Slide11Frequency and Period
They are reciprocals of each other therefore,
frequency
= number of cycles / total time
Period = total time / number of cycles
Slide12Amplitude
The distance from rest position to maximum displacement is the amplitude
Slide13Check Your Understanding
A mass hung from a spring vibrates 15 times in 12 s. Calculate
the frequency.
the period of the vibration.
Answer: a) f = 1.2 Hz b) T = 0.80 s
Slide14Check Your Understanding
A child is swinging on a swing with a constant amplitude of 1.2 m. What total distance does the child move through horizontally in 3 cycles?
Answer: 14.4 m
Slide15A Few More Terms
CrestsHigh section of the wave
Troughs
Low section of the wave
Wavelength (in m)Distance from crest to crest or from trough to trough
Slide16Universal Wave Equation
Recall:Regarding waves, the distance traveled is the wavelength (
λ
in m’s) and the time is the period (T) which is the time to compete a wavelength in s therefore,
The wave equation works for all waves, visible and invisible.
Slide17Check Your Understanding
The wavelength of a water wave in a ripple tank is 0.080 m. If the frequency of the wave is 2.5 Hz, what is its speed?
Answer: 0.20 m/s
Slide18Check Your Understanding
The distance between successive crests in a series of water waves is 4.0 m, and the crests travel 9.0 m in 4.5 s. What is the frequency of the waves?
Answer: 0.50 Hz
Slide19Check Your Understanding
The period of a sound wave from a piano is 1.18 × 10–3
s. If the speed of the wave in the air is 3.4 × 102 m/s, what is its wavelength?
Answer: 0.40 m