2 General Wave Properties describe what is meant by wave motion as illustrated by vibration in ropes, springs and experiments using a ripple tankstate what is meant by the term wavefrontshow understanding that waves transfer energy without transferring matterdefine speed, frequency, wavelength, period and amplituderecall and apply the relationship velocity = frequency x wavelength to new situations or to solve related problemscompare transverse and longitudinal waves and give suitable examples of each
3 Wave Wave is the product of a vibration Two types of wave: transverse and longitudinal
4 WaveDuring wave motion, particles vibrate about their fixed position and the waveform progresses (travels).Transverse waves: particles vibrate perpendicular to wave motion eg. Light wave, water rippleLongitudinal waves: particles vibrate parallel to wave motion eg sound wave.
6 Wave (Longitudinal Wave) wavelengthwavelengthrarefactioncompressionCompression: region of high pressureRarefaction:Region of low pressuredistancepressurecompressioncompressionrarefactionrarefaction
7 Wave Frequency, f – number of oscillations per second <Hz> Period, T – time taken for one oscillation <s>Wavelength, – distance between two consecutive particles in phase. <m>
8 WavesExampleThe diagram below shows a transverse wave moving to the right.a)In which direction will the particle T and V move?b) Which particle is in phase with T?WQRUSVXTY
9 Wave (cont’d) W Q R U S V X T Y Particle T moves upwards; V moves downwards.Particle X is in phase (in step) with particle T.
10 Wave Relationship between frequency, f and period, T SI unit for frequncy, f: HzSI unit for period, T: s
11 WaveRelationship between wave speed, v; frequency, f and wavelength, SI unit for speed, v: ms-1v = f
12 WaveExampleTransverse waves are produced in a long rope by moving one end from side to side. The frequency of the wave is 2Hz.a) What do you mean by 2Hz?b) What is the wavelength if the speed of the wave is 0.5ms-1?
13 Wave a) What do you mean by 2Hz? Each particle on the rope oscillates 2 cycles per secondb) What is the wavelength if the speed of the wave is 0.5ms-1?v = f x 0.5 = 2 x = 0.5/2= 0.25m
14 WaveThe speed of the wave motion, v is related to its frequency, f and wavelength through the equation:The frequency of the wave is related to the period of vibration, T through:v = f f T = 1
15 Wave Distance/m displacement/m 2 4 6 Wavelength, = 4m v = f x 246Wavelength, = 4mv = f x = 0.5 x 4= 2ms-1time/sdisplacement/m123Period, T = 2sFrequency, f = 0.5Hz
16 WaveThe displacement time graph of a transverse wave is shown in the figure below. Its wavelength is 3m.Calculatethe speed of the wavethe time taken for the wave to travel a distance of 3000kmDisp/ 10-5m0.30.71.2time/10-5ms188.8.131.52
17 Wave a) v = f = [1/(1 x 10-5 x 10-3) ]x 3 = 3 x 108 ms-1 Disp/ 10-5m0.30.71.2time/10-5ms184.108.40.206a) v = f = [1/(1 x 10-5 x 10-3) ]x 3= 3 x 108 ms-1b) t = 3000 x 1000 / 3 x 108= 100 sT = ( ) 10-5ms= 1 x 10-5 x 10-3 s
18 Wave What is a wavefront? Source:http//www.physicscentral.comWhat is a wavefront?Wavefront is a line that joins all the points (usually the crests) on the wave that are in phaseWavefront is likened to the bird’s eye view of a wave.Changes in wavefront indicates changes in speed of wave or presence of underwater features
20 Waves Frequency d Medium (density / depth etc) Speed 123As the wave approaches a shallower region, the speed of the wave reduces due to larger resistive forces .FrequencydMedium (density / depth etc)SpeedSource of vibration
21 This is due to the shallower sea bed near the beach Smaller wavefronts as the wave approaches shows the decrease in speed of the wave.This is due to the shallower sea bed near the beachSource//http:www.nasaimages.org
22 Wave bends towards normal large wavelengthUnderstanding refractionwaterglassWave bends towards normalshort wavelengthWave slows down when entering denser medium, experiencing higher resistance
23 Conclusion Wave motion is the result of vibrations. There are two types of waves: transverse and longitudinal.Wave travels as the particles vibrate about their fixed positions.Relationship v = f x us to determine the speed of wave.The wavefront tells us direction of travel and their distance between tells us the wavelength.Changes in wavefront gives us an indication of changes in wave medium.