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General Wave Properties

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describe what is meant by wave motion as illustrated by vibration in ropes, springs and experiments using a ripple tank describe what is meant by wave motion as illustrated by vibration in ropes, springs and experiments using a ripple tank state what is meant by the term wavefront state what is meant by the term wavefront show understanding that waves transfer energy without transferring matter show understanding that waves transfer energy without transferring matter define speed, frequency, wavelength, period and amplitude define speed, frequency, wavelength, period and amplitude recall and apply the relationship velocity = frequency x wavelength to new situations or to solve related problems recall and apply the relationship velocity = frequency x wavelength to new situations or to solve related problems compare transverse and longitudinal waves and give suitable examples of each compare transverse and longitudinal waves and give suitable examples of each

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Wave Wave is the product of a vibration Wave is the product of a vibration Two types of wave: transverse and longitudinal Two types of wave: transverse and longitudinaltypes

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Wave During wave motion, particles vibrate about their fixed position and the waveform progresses (travels). During 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 ripple Transverse waves: particles vibrate perpendicular to wave motion eg. Light wave, water ripple Longitudinal waves: particles vibrate parallel to wave motion eg sound wave. Longitudinal waves: particles vibrate parallel to wave motion eg sound wave.

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Wave (Transverse Wave) crest trough crest amplitude wavelength

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Wave (Longitudinal Wave) rarefaction compression wavelength distance pressure compression rarefaction Compression: region of high pressure Rarefaction: Region of low pressure

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Wave Frequency, f – number of oscillations per second Frequency, f – number of oscillations per second Period, T – time taken for one oscillation Period, T – time taken for one oscillation Wavelength, – distance between two consecutive particles in phase. Wavelength, – distance between two consecutive particles in phase.

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Waves Example The 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? W Q R U S V X T Y

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Wave (cont’d) W Q R U S V X T Y a)Particle T moves upwards; V moves downwards. b)Particle X is in phase (in step) with particle T.

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Wave Relationship between frequency, f and period, T Relationship between frequency, f and period, T SI unit for frequncy, f: Hz SI unit for frequncy, f: Hz SI unit for period, T: s SI unit for period, T: s

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Wave Relationship between wave speed, v; frequency, f and wavelength, Relationship between wave speed, v; frequency, f and wavelength, SI unit for speed, v: ms -1 SI unit for speed, v: ms -1 v = f

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Wave Example Transverse 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 ?

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Wave a)What do you mean by 2Hz? Each particle on the rope oscillates 2 cycles per second b)What is the wavelength if the speed of the wave is 0.5ms -1 ? v = f x v = f x 0.5=2 x 0.5=2 x =0.5/2 =0.5/2 = 0.25m

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Wave The speed of the wave motion, v is related to its frequency, f and wavelength through the equation: The 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: The frequency of the wave is related to the period of vibration, T through: v = f f T = 1

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Distance/m displacement/m 0 246 Wavelength, = 4m time/s displacement/m 0 123 Period, T = 2s Frequency, f = 0.5Hz Wave v = f x = 0.5 x 4 = 2ms -1

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Wave The displacement time graph of a transverse wave is shown in the figure below. Its wavelength is 3m. Calculate a) the speed of the wave b) the time taken for the wave to travel a distance of 3000km Disp/ 10 -5 m 0.3 0.7 1.2 time/10 -5 ms 1.72.2 2.7

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Wave a) v = f a) v = f = [1/(1 x 10 -5 x 10 -3 ) ]x 3 = 3 x 10 8 ms -1 b) t= 3000 x 1000 / 3 x 10 8 = 100 s Disp/ 10 -5 m 0.3 0.7 1.2 time/10 -5 ms 1.72.2 2.7 T = (1.7 - 0.7) 10 -5 ms x 10 -5 x 10 -3 s = 1 x 10 -5 x 10 -3 s

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Wave What is a wavefront? What is a wavefront? Wavefront is a line that joins all the points (usually the crests) on the wave that are in phase Wavefront 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 Source:http//www.physicscentral.com

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wavelength direction

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Waves 1 2 3 n Frequency d Medium (density / depth etc) Medium (density / depth etc) Speed d Source of vibration Source of vibration As the wave approaches a shallower region, the speed of the wave reduces due to larger resistive forces.

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Source//http:www.nasaimages.org Smaller wavefronts as the wave approaches shows the decrease in speed of the wave. This is due to the shallower sea bed near the beach

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Wave water glass large wavelength short wavelength Wave slows down when entering denser medium, experiencing higher resistance Wave bends towards normal Understanding refraction

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Conclusion Wave motion is the result of vibrations. Wave motion is the result of vibrations. There are two types of waves: transverse and longitudinal. There are two types of waves: transverse and longitudinal. Wave travels as the particles vibrate about their fixed positions. Wave travels as the particles vibrate about their fixed positions. Relationship v = f x us to determine the speed of wave. 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. 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. Changes in wavefront gives us an indication of changes in wave medium.

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